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General Information => FAQ/Tech Tips/Please Read First => Topic started by: regcheeseman on April 18, 2006, 06:36:36 am

Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: regcheeseman on April 18, 2006, 06:36:36 am
Originally dealt with in this thread http://www.vwdiesel.net/forum/index.php?topic=3096.0 (http://www.vwdiesel.net/forum/index.php?topic=3096.0), now condensed into the various solutions to convert all type of VW gas type revcounters to work from the W terminal on VW fitment altenators.

The original gasser schematic
(http://i492.photobucket.com/albums/rr281/regcheeseman/tachomods/final_gasser.jpg)


Re-worked into diesel w terminal version
(http://i492.photobucket.com/albums/rr281/regcheeseman/tachomods/final_diesel.jpg)

First up the VDO unit...

The gasser board before (http://i492.photobucket.com/albums/rr281/regcheeseman/tachomods/GasserPCB.jpg)

replace R1 with 100 ohm
leave R2  
replace R3 with wire link
replace R4 with 191 ohm
replace R5 with wire link
replace R6 with 10K
replace R7 with 15K

 
replace C1 with 10nF
remove C2
leave C3
remove C4
replace C5 with 47nF
fit C6 3.3uF in vacant spaces next to tacho motor (red and blue) wires or desolder wires from board, fit cap and then solder wires to cap wires/board.

adjust RV1 to mid range

The final working board.
(http://i492.photobucket.com/albums/rr281/regcheeseman/tachomods/final_board.jpg)

Note the two resistors joined together are because I could not find a 191 ohm resistor so joined a 180 and a 10.

C6's value is not critical, I used a 2.7 instead of a 3.3, it works fine without this cap altogether and I believe is only there to stop needle flutter (I didn't have a problem with or without this fitted)


Mods for westmoreland clocks...

First the schematic as is..
(http://i492.photobucket.com/albums/rr281/regcheeseman/tachomods/morts_gasser.jpg)

The annotated board..
(http://i492.photobucket.com/albums/rr281/regcheeseman/tachomods/gastachboard2ann.jpg)

A lot of similarities with the original VDO circuit, I'll wager the SAK chip is the same and converting to the diesel tacho circuit should work..

Make R1 = 100ohm
replace R2 with 72ohm
replace R3 with wire link
replace R4 with 191ohm
replace R5 with wire link
replace R6 with 10K
replace R7 with 15K

replace C1 with 10nF
leave C3
remove C4
remove C?


make RV1 = 22K
remove RV2 and replace with 47nF cap

If you can get a 3.3uF across the needle output wires then do so....it's not critical though.



Now the Motometer clocks...

(http://i492.photobucket.com/albums/rr281/regcheeseman/tachomods/johnnypcb9yw.jpg)

(http://i18.photobucket.com/albums/b109/joeallison_99/TDI%20ENGINE/100_2262.jpg)

(http://i492.photobucket.com/albums/rr281/regcheeseman/tachomods/Ive_lost_biobillpcb.jpg)

Swap R1 for 15K
Remove R2
Remove R3
Swap R4 for 191 ohm
Swap R5 for 72 ohm
Swap R6 for 100 ohm
Swap R7 for 10K

Replace zener with wire link

Swap C1 for 10nF
Swap C2 for 47nF (nanofarad)
Swap C3 for 47uF (microfarad)
Swap C4 for 3.3uF

If replacing C3 or C4 with electrolytics then observe polarity as marked on board.

Leave the terminal marked ZA disconnected where appropriate.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on February 01, 2007, 07:51:07 pm
this should help anyone doing a gti tach:

Quote from: fatmobile
That is a very nice tiltisorie ... bad spelling I'm sure but it tilts the car up on it's side nicely. I've been eyeing a few on the vortex and this one looks great compared to some of them.
 I was messing with the '83 westmoreland tach, figuring what parts I need to source.
 It looks like there are a few resistors that can be moved from one spot to another.
 R6 is a 15K resistor and can be moved down to where R7 is. Then a 10K is used in the R6 spot.
 R3 needs to be a wire link and is a 100 ohm now. On the diesel tach, R1 needs a 100 ohm resistor so that can be used there.
  Actually I'm thinking the R1 resistor determines how far the needle swings so I might put a variable resistor in there and see if I can get it to work with the stock gas tach face and go to 7000RPM.
 The stock R1 resistor in the gasser tach is about 10ohm (it was 15ohm in my '91 Golf gasser tach) so I might even keep that one in there.
(http://img218.imageshack.us/img218/5563/gastachboard2ann7hh.th.jpg) (http://img218.imageshack.us/my.php?image=gastachboard2ann7hh.jpg)
 ...so the parts list looks like:
10K resistor
 72ohm resistor
191ohm resistor
 and a 10nf cap (the '91 Golf already has a 10nf cap that is getting removed)
 4 little pieces
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Black Smokin' Diesel on March 15, 2007, 07:27:36 pm
If I were to use a CE1 golf/jetta MK2 8v gasser tach to convert to diesel use, which schematic would I use?
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on March 18, 2007, 01:50:48 pm
try to find the one thats closest to the board you have, they are all so different and there are so many of them
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Black Smokin' Diesel on March 19, 2007, 08:49:50 pm
Allright I'll grab one from the junker and go from there. Maybe I'll bring a print of these with me and try to get one as close to the ones in this thread.

Thanks a lot.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitGTDguy on November 27, 2007, 10:48:16 am
Another SUCCESS for this FAQ. I was able to convert an early Mk1 (round) VDO tachometer to W terminal with success in the last couple of days. I was even able to easily calibrate it on the b3 16v's 90amp alternator as it has an active W terminal.
No fluctuations and very little adjustment. All adjustment was able to be done at the potentiometer itself...

Good stuff...maybe I'll post a picture of the modified board here in the next few days. My soldering skills are rusty, but getting better I guess...some pretty creative wrapping and and installation a few components in a series.

Also, I did not install the 3.3uF inline of the tacho output wires... haven't seen any problems as of yet.

Joe
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: [email protected] on December 02, 2007, 11:05:36 pm
Could someone help me please? I need to know what to do for this:

http://www.vwdiesel.net/phpBB/viewtopic.php?t=11404
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitGTDguy on December 17, 2007, 10:04:01 pm
More Proof!!! Posted in my thread as well...but this is good here too!!!

Finally,  got a chance to start up the mTDI Rabbit again here today. After fixing the dowpipe, etc. etc. and getting the exhaust hooked back together all is well. Just hadn't had the time
Also, I was able to full intergrate the tach into the early dash, I even used the factory german cluster plug and was able to change out the connections needed for a "factory" hookup and look so that I didn't have to tape off terminals, add connections, etc. The early MK1 cluster plugs are actually really nice to work with, They come apart EASY which makes swapping connections really easy as well. I ended up switching to the motormeter circuit sheet that I had as the VDO one was pretty bad. After comparing them though I didn't see any major differences, etc. and everything is good to go!

Idles a bit high. at about 1.5k and I don' t think the engine is actually idling that high so I think that accounts for the difference in between the pulleys on the test/calibration car (my 16v b3 gasser ) and the mTDI engine running serp belts and the 2.0 90amp alternator.
Easy enough to fix though...

Here are a few pics...as promised...
(http://i18.photobucket.com/albums/b109/joeallison_99/79%20Rabbit%20DD/100_3230.jpg)
(http://i18.photobucket.com/albums/b109/joeallison_99/79%20Rabbit%20DD/100_3232.jpg)

Had that second one revved quite a bit higher...but my digi cam recycle time SUCKS.... either way. No flutter, etc. I'm going to need to find another "VDO" parts tach for a good needle (as this ones paint is damaged and/or do something with the needles. The biggest drawback I think with the older gauges is the illumination itself...
Hmm...maybe an LED project in the future!!!
Either way...WORKING CONVERTED GASSER TACH!!! WAHOO!!!

Joe
Title: GTI tach
Post by: coalminer16 on February 14, 2008, 08:38:51 pm
I just got two tachs wired up for both of my rabbits and neither of them are the correct rpm. They both idle at 2000 rpm. Any pointers I used the correct resistors. I may have the wrong caps in the system (due to converting). Would this be the problem or do I just need to get a variable resistor. Can I put the variable resistor on the input line if that is the only way to correct it. Any suggestions let me know please. I did everything exact but the optional caps on the two wires going to the needle. Maybe I need a higher resistor value somewhere. Doesn't jump around though (the needle). Thanks
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: prothe on February 16, 2008, 09:12:58 pm
This is really good stuff.  Thanks!
Title: Answer as to why my rpm changes
Post by: coalminer16 on March 05, 2008, 09:04:28 pm
I posted that a 5.6 k resistor makes the rpm correct at start up but changes by about half if I drive interstate speed. I don't think it does it in town but I haven't driven it long enough to know. I asked my Electrical Engineering friend/previous teacher and he said that it might have a "cold connection" is what I think he put it as (I am Mechanical Engineering so he has the better understanding on this part). He explained that as a person solders the resistors and caps on, if the ends of the wire moves before total cool down of the solder then it won't have a perfect connection. So after a while the connection will heat up because of this and the resistance of the solder actually changes. Long story short he said if you can get the metal flowing really good and have the wire end in the pool of metal and then take the heat source off and not drag it off (in a sweep motion, like welding with wire or arc almost) then it will prevent some of the cold connections. But because this is a small circuit board that is the old style with solder connections this will be hard anyways. Bottom line I have something that if I factor if the engine is warm or cold I know roughly the rpm and it looks nice and factory installed looking. Plus now I can see the temp gauge better if I am leaning forward on the steering wheel on some of those long drives (not uncommon I drive 24 hr strait-Spring break, SD to Vancouver to Mexico and back in 9 days with 4 days skiing). Hope this helps.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: rallydiesel on April 20, 2008, 04:54:51 pm
Good thread.  :oops:
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on May 22, 2008, 09:55:23 pm
i just got another one of these put together last night, its a north american gti tach in my 81 rabbit,  works great! and looks great. 1 thing that i found is that if you use a permanent marker to color say the 5000rpm mark and all the marks after that red, it makes it pretty much impossible to read at night since the paint vw used must have some kind of reflective *** in it.  oh well it looks good during the day haha, i'll post pictures tomorrow.  oh yeah the other thing that pissed me off about it was that i put a gti 120mph speedo in it since my old odometer didn't work, and of course my new one goes to roll over 985999.9 and gets stuck just like my old one haha, i guess i'll be ripping it all back apart soon enough.


i may stick the old speedo back in... since it has the right mileage


(http://img.photobucket.com/albums/v306/Trev0rbr/DSCN0542.jpg)
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Krazy on July 30, 2008, 04:42:07 pm
Do you have an easy way to get the cluster out of the dash?  I have trouble getting the cable unhooked from the cluster.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: stuvy on July 31, 2008, 08:50:44 pm
Once the tach is moded, is it a straight put in the dash ordeal. Or do I need to run new wires?
I am working on a 82 rabbit FYI.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: stuvy on August 01, 2008, 03:59:14 pm
From what I can tell you need to run a wire from the W terminal to the cluster. I am still waiting for my MK1 bentley to arrive in the mail.
So I guess my question becomes what terminal do I run the wire too?
The tachometer in question is an 83 Westmoreland GTI cluster.
Thanks in advance.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on August 07, 2008, 06:41:47 pm
Quote from: "stuvy"
Once the tach is moded, is it a straight put in the dash ordeal. Or do I need to run new wires?
I am working on a 82 rabbit FYI.


You need to run a wire from the w terminal to the cluster, i spliced mine in with wire number 5 per the bently, if i recall right.  u could also just crimp one of the circular electrical connectors on the end of your new wire and put it on the signal post on the back of the tach.  if you have a rabbit with the dynamic oil light then none of this is necessary, but i don't believe that was introduced until 1983
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on August 07, 2008, 06:42:40 pm
Quote from: "Krazy"
Do you have an easy way to get the cluster out of the dash?  I have trouble getting the cable unhooked from the cluster.


hey usually what i do to get the speedo cable off is i lay on my back and reach up in front of the fuse panel and grab the cable and take it off that way, it seems to work well, another thing you could try is removing the speaker, i think that lets u reach behind it as well, but i'm not sure since i never did it that way.  also theres a button on the bottom of the headlight switch that releases the switch knob.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: stuvy on August 07, 2008, 11:49:09 pm
Quote from: "Trev0rbr"
Quote from: "stuvy"
Once the tach is moded, is it a straight put in the dash ordeal. Or do I need to run new wires?
I am working on a 82 rabbit FYI.


You need to run a wire from the w terminal to the cluster, i spliced mine in with wire number 5 per the bently, if i recall right.  u could also just crimp one of the circular electrical connectors on the end of your new wire and put it on the signal post on the back of the tach.  if you have a rabbit with the dynamic oil light then none of this is necessary, but i don't believe that was introduced until 1983


Yeah I am working with a cluster from an 83-84 I forget at the moment. Thanks for the info, I'll try and get this thing to work. So it should just be a plug and play thing, with 1 connection on the number 5 wire?
Thanks.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on August 08, 2008, 01:18:30 am
yeah i'm not sure exactly which wire it is tho, check the bentley
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: 53 willys on September 07, 2008, 02:48:34 pm
anybody else having trouble seeing the pics in the first post??
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: zukgod1 on September 08, 2008, 05:37:24 pm
I dont see anything either.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Smokey Eddy on September 08, 2008, 06:26:13 pm
i wish very much that these photos were still here :(
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: blkboostedtruck on September 08, 2008, 08:58:29 pm
is there a way to get them back through archives?
Duane
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: 53 willys on September 10, 2008, 09:34:58 pm
Quote from: "libbybapa"
I have the thread as a pdf with all images intact.  Anyone want to host it?

Andrew

I dont know how or if I can host it????
but you could email it to me right???
Title: UK Tachometer Conversion
Post by: daveo on September 19, 2008, 10:09:54 am
Hi there, sifting through this article about the conversion of stock VW VDO Tachometers to run on a Diesel.

I have a 1.6 N/A fitted to my '82 Jetta with an alternator from a 1991 Diesel Caddy. I have a standard Mk1 Tacho-when I connected the input of this directly to the W-Terminal on the alternator i got a reading of about 6000RPM (at idle!!). Using the trimmer on the back I was able to get this down to about 4000RPM and at both times the readouts seemed to increase roughly corresponding to the engine speed.

My Question: By installing another Variable Resistor and fine trimming it will I be able to get an accurate read-out on the Tacho or not, and will it cause damage to the tacho itself?  :?

Any help will be much appreciated!

Dave
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: 79rabbit4dr on October 31, 2008, 06:39:26 pm
I'm thinking about buying this unit (think it's from a GTI) for $20, will it work in my 81 1.6l na or is there a better one I should buy?

(http://farm4.static.flickr.com/3243/2985764308_bdcaa05b81.jpg)

here is the cluster I have right now.

(http://lh5.ggpht.com/_9S7ulOGt3r8/SQuEu4DeRlI/AAAAAAAABNw/K66UlZWonkI/s800/DSC07067.JPG)
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: lord_verminaard on November 03, 2008, 02:45:01 pm
Quote from: "libbybapa"
click to download (http://www.filefactory.com/dlf/f/c097dc/b/7/h/142db973b95a0c2ada0e349fbc88507c/j/0/n/Gas_Tach_Conversion_pdf)

See if that works.  Cheers.

Andrew


Try this one instead:
http://www.filefactory.com/file/c097dc/n/Gas_Tach_Conversion_pdf

Thanks!
Brendan
Title: using gasser tach with inductive pickup.....
Post by: jimbote on November 29, 2008, 05:10:27 pm
tried this today....gonna keep posted on the workability....basically hooked up an 83 GTI tach to a battery and a ford V8 distributer....no coil no module....just the inductive pickup and trigger wheel....with my 750 rpm drill at full blast the tach registered just under 3K....and was smooth down to almost zero rpm....so I cut six of the trigger "arms" off of the wheel leaving two at 180 apart and buzzed the drill up to full speed...the tacho was smooth reading around 500 rpm....probably could be adjusted out with the pot.....I have already built a bracket to house an inductive speedo pickup from a late model ford tranny....it will be pointing at the four balancer bolts at the front of the crank....two of which will be spaced out so as to trigger the sensor only twice per rev....I'll be working this manana and I'll keep posted (with pics)  but looks promising so far :D
Title: Re: using gasser tach with inductive pickup.....
Post by: jimbote on November 30, 2008, 04:46:32 pm
Quote from: jimbote
tried this today....gonna keep posted on the workability....basically hooked up an 83 GTI tach to a battery and a ford V8 distributer....no coil no module....just the inductive pickup and trigger wheel....with my 750 rpm drill at full blast the tach registered just under 3K....and was smooth down to almost zero rpm....so I cut six of the trigger "arms" off of the wheel leaving two at 180 apart and buzzed the drill up to full speed...the tacho was smooth reading around 500 rpm....probably could be adjusted out with the pot.....I have already built a bracket to house an inductive speedo pickup from a late model ford tranny....it will be pointing at the four balancer bolts at the front of the crank....two of which will be spaced out so as to trigger the sensor only twice per rev....I'll be working this manana and I'll keep posted (with pics)  but looks promising so far :D


OK this works like a charm!!! :D .....for anyone not wanting to solder new caps or resistors on your tach this will work and give an accurate tacho signal with no mods to the tach or calibration of the tach for that matter.....some things I changed from my original idea of pointing the sensor at the pulley bolts was to use two 3/8 nuts welded to the outside of the crank pulley exactly 180 apart and have the sensor pointed at the nut facet with about .020 clearance....the old idea simply had too much bracket hanging over the sprocket add to that thrust clearance variance and it may have thrown off the gap and thus the reading.....good luck!!

(http://i146.photobucket.com/albums/r262/jimbote/tachsender005.jpg)

(http://i146.photobucket.com/albums/r262/jimbote/tachsender002.jpg)

(http://i146.photobucket.com/albums/r262/jimbote/tachsender003.jpg)


(http://i146.photobucket.com/albums/r262/jimbote/tachsender004.jpg)

(http://i146.photobucket.com/albums/r262/jimbote/tachsender006.jpg)
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: blkboostedtruck on November 30, 2008, 04:53:36 pm
pics!!! :D  and are you taking orders on? :D
Duane
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on November 30, 2008, 05:40:09 pm
Quote from: "blkboostedtruck"
pics!!! :D  and are you taking orders on? :D
Duane


Ha ha....yeah place your orders now!!!....this should be simple and straight forward enough for anyone with a cutoff wheel a drill press and a mig to accomplish with ease....as far as the wiring very simple....one leg of the sensor goes to the tacho input....one goes to ground....of course you need battery positive and ground to the tach.....Ohh yeah....I have a dakota digital tach converter I'd like to get $60 shipped lower four eight...i've never hooked it up only took it out of the box and and read the instructions..... :D
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: blkboostedtruck on November 30, 2008, 06:59:13 pm
yep jimbote very nice! what would you need for all the parts? i can take care of the welding here! i have a MIG welder in the garage!
Duane
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on November 30, 2008, 08:44:32 pm
Don't have a part number right now...but the sensor I used came from a T45 mustang transmission....my pop rebuilds T5's and T45's so he has   parts "laying" around.....I think the year model would be a 2001 mustang V8....but I think the late model T5's and 3650's have the same sensor....it has to the be a tranny with the reluctor wheel on the output not the gear driven sensor as on some earlier models....now I think you can get any inductive sensor to work even the smaller ones because of the speed at the crank pulley mine was generating 1.2 volts AC at idle....you can even make the inductive sensor from a distributor work....inductive pickups are commercially available


http://store.summitracing.com/egnsearch.asp?Ntt=vdo+340+020&searchinresults=false&Ntk=KeywordSearch&DDS=1&N=700+115

....but there is no need to spend fifty quid on a sensor....as for the bracket....3/16 X 1" strap cut drilled and tapped for the sensor hole and sensor hold down bracket....I attached the bracket to the front of the block using two available bolt holes (early will be 7mm late will be 8mm)....also make sure you leave enough "slop" in the bolt holes to allow for gap adjustment.....the bracket needs to be relatively stiff so as to avoid vibrational contact with the "poles" ie nuts....again have fun and report back!!!
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: saurkraut on December 01, 2008, 09:31:53 am
Does the Ford probe have its own signal conditioner?  IE you hooked 12 volts up to it, and it puts out the wave signal when the crank is turning, at a lower voltage.

I don't know if that VDO probe will drive the VW tach, as I suspect the VDO speedometer sends a couple volts to the VDO probe, and the probe switches it on and off.

The Ford probe may be the better choice for driving the VW tach with out extra electronic stuff. (technically speaking)
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on December 01, 2008, 10:10:25 am
Quote from: "saurkraut"
Does the Ford probe have its own signal conditioner?  IE you hooked 12 volts up to it, and it puts out the wave signal when the crank is turning, at a lower voltage.

I don't know if that VDO probe will drive the VW tach, as I suspect the VDO speedometer sends a couple volts to the VDO probe, and the probe switches it on and off.

The Ford probe may be the better choice for driving the VW tach with out extra electronic stuff. (technically speaking)


If you have a sensor that takes voltage and sends back a switched signal then that is a "hall effect" switch....this sensor(the ford speedo sensor) and all "inductive" sensors produce current with no needed voltage input only a bit a metal passed through the magnetic field will "move" electrons in the windings around the magnet....in this application there is NO external voltage going to the probe, that would probably prove destructive to the probe itself IE complete meltdown or at best a non functioning part.....Not sure what VDO probe you refer to but if it is an inductive probe it should work
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on December 01, 2008, 09:30:18 pm
Quote from: "saurkraut"
Does the Ford probe have its own signal conditioner?  IE you hooked 12 volts up to it, and it puts out the wave signal when the crank is turning, at a lower voltage.

I don't know if that VDO probe will drive the VW tach, as I suspect the VDO speedometer sends a couple volts to the VDO probe, and the probe switches it on and off.

The Ford probe may be the better choice for driving the VW tach with out extra electronic stuff. (technically speaking)



OK I feel dumb.....to answer your question about the VDO unit it will drive the tacho....the one in the link is an "inductive" pickup the same one Dakota digital recommends for their diesel tach converter....it does NOT recieve any voltage from the tach to operate....and yes this unit is used for tachs speedos etc.....I guess I failed to notice that the link I provided was actually a VDO unit I was assuming it was generic.... :oops:
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Smokey Eddy on December 01, 2008, 09:58:57 pm
This is probably written somewhere but I've tried searching with no sucess.
I assume the W signal puts out 12V? I put a voltmeter to it and spun it by hand (its off the car right now) and i got a good solid 12v but there was some very strange behavior of the needle before it stabalized. can anyone verify 12V output of the w terminal? If it's already posted just pm me please  :oops:
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Vincent Waldon on December 01, 2008, 11:10:55 pm
Square wave:

(http://i197.photobucket.com/albums/aa85/vwaldon/Wterm_1100RPM_distance_web.jpg)

8 volts AC:

(http://i197.photobucket.com/albums/aa85/vwaldon/voltmeteronWterminal_web.jpg)
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: saurkraut on December 02, 2008, 09:40:09 am
Quote from: "jimbote"
If you have a sensor that takes voltage and sends back a switched signal then that is a "hall effect" switch....this sensor(the ford speedo sensor) and all "inductive" sensors produce current with no needed voltage input only a bit a metal passed through the magnetic field will "move" electrons in the windings around the magnet....in this application there is NO external voltage going to the probe, that would probably prove destructive to the probe itself IE complete meltdown or at best a non functioning part.....Not sure what VDO probe you refer to but if it is an inductive probe it should work


Okydokes,

The Ford probe (with no voltage applied) can drive the VW 4 cylinder gas engine tach and produce an accurate RPM if it sees two chunks of steel every rotation of the crank shaft.

True or no

does the Ford probe have only two wires (signal and ground)?
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on December 02, 2008, 10:00:51 am
Okydokes,

The Ford probe (with no voltage applied) can drive the VW 4 cylinder gas engine tach and produce an accurate RPM if it sees two chunks of steel every rotation of the crank shaft.

True or no

does the Ford probe have only two wires (signal and ground)?[/quote]

True.....the ford probe and "most" magnetic inductive sensors (found in automotive applications) have only two wires that are interchangeable signal or ground as in it does not matter which wire goes to ground and which wire goes to signal....the two leads or pins in "most" sensors are only the termination of a coil of copper windings around a magnet....now all "inductive" sensors do not have a "magnet" some are merely a coil of windings around a laminated core and the moving poles are magnets ie the magneto on a lawn mower.....but for this application it would probably be easiest to source and use a "magnetic inductive" pickup ....being as how it can be difficult to attach magnets to the crank pulley....
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Smokey Eddy on December 02, 2008, 02:03:20 pm
Quote from: "Vincent Waldon"
Square wave:

(http://i197.photobucket.com/albums/aa85/vwaldon/Wterm_1100RPM_distance_web.jpg)

8 volts AC:

(http://i197.photobucket.com/albums/aa85/vwaldon/voltmeteronWterminal_web.jpg)



What kind of alt do you have? Maybe we have different ones?
I got a very solid 12v
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Vincent Waldon on December 02, 2008, 03:03:23 pm
The W signal is the W signal... a square wave from the diode bridge in the alternator that varies in frequency... which is what the tachometer translates into RPM.  All 12V alternators with the same number of stator windings will have pretty much identical signals.... although different size alternator pulleys will result in different calibrations.

Your DC voltmeter will try its best to approximate the peaks of this square wave (and the peaks do go to around 12V on the scope, as luck would have it!) and various meters will do a better job than others... particularly if the frequency is low (as in, turning the alternator by hand) but the important thing is that it's the frequency that varies with RPM, not the voltage.

Same thing actually with a gasser BTW... the frequency of the signal from the points/hall effect transducer to the coil (which is where the tach is connected) varies with RPM, but the voltage to the coil is the same boring ground it always is.   :wink:

Clear as mud, right ??!!

The other possibility is that you're reading the D+ terminal rather than the W terminal... the D+ line will show you a steady 12V at all times (assuming the BAT light isn't burnt out !).
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on December 04, 2008, 08:46:47 pm
Just wanted to say I drove the caddy all day and not even a blip out of the tacho...it works perfect....also when choosing an inductive pickup for this mod I would recommend one that will put out at least a 1VAC I tried others that put out less (much smaller ones) they put out from .3 to .5 VAC and they would not drive the test tacho.....distributor mounted inductive coils seem to work great and they are CHEAP!!! ie...everywhere!!!
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Smokey Eddy on December 05, 2008, 12:23:31 am
What im trying out which is an extreme poor man's method is...
im making a flip flip out of three "D-latch"s that will divide the frequency the W terminal puts out by 8.

It's a crude method i know, but the micro controller is to come later.  :roll:

I  bought 2 paired d-latches for about $1.43 each(you only need three so one is going to be unused).  Chip mounts, a piece of bread board and some soldering later and you're good to go.
Make a case for it and bolt it in the engine bay somewhere. Run the w terminal straight to it (as they can handle up to 15V) and then straight to an aftermarket  tach. Dunno if this works yet as my engine isn't running but i WILL make a thread about it.

Just my ideas for what they're worth. (in the tuning world, worth nothing :P in the "keeping my vw diesel alive for pennies" world, invaluable)
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Vincent Waldon on December 05, 2008, 01:05:37 am
This is great stuff Eddy... looking forward to what you come up with.

When I looked at this back when I took the pictures I couldn't convince myself that divide-by-8 would  work because of the pulley diameters, etc...  more like you might need divide-by-7.456, but a simple re-cal of the gasser tach would fix that I bet.  A microprocessor makes this easier, of course... but if a few latches will do then go for it !!
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Smokey Eddy on December 05, 2008, 04:27:21 am
Well that's the thing vince.

Latches will do, but only to an extent right. A micro controller would be "perfect" but latches would be a good guess.  haha ... so ... when i get it going and it says im idling at 200 rpm i'll know it won't work :P  but if its like 50rpm out i won't care.
Title: inductive pickup part number.....
Post by: jimbote on December 05, 2008, 03:48:20 pm
OK....at the behest of others interested....here is the part number of the Ford inductive pickup I used for my tacho conversion........................... XR3Z-7H103AB ....retails for $23.90 stateside....as far as I know this pickup can be found on all 99' and newer T5's, T45's, and 3650 manual transmissions used in Ford Mustangs....have fun!!
Title: Re: inductive pickup part number.....
Post by: saurkraut on December 05, 2008, 05:13:31 pm
Quote from: "jimbote"
OK....at the behest of others interested....here is the part number of the Ford inductive pickup I used for my tacho conversion........................... XR3Z-7H103AB ....retails for $23.90 stateside....as far as I know this pickup can be found on all 99' and newer T5's, T45's, and 3650 manual transmissions used in Ford Mustangs....have fun!!


Thanks!

So this puppy can drive a standard VW gas tach with no calibration?

I'd rather measure the real RPM then read "a rpm" that comes from the alternator.
Title: Re: inductive pickup part number.....
Post by: Smokey Eddy on December 05, 2008, 06:37:46 pm
Quote from: "saurkraut"
Quote from: "jimbote"
OK....at the behest of others interested....here is the part number of the Ford inductive pickup I used for my tacho conversion........................... XR3Z-7H103AB ....retails for $23.90 stateside....as far as I know this pickup can be found on all 99' and newer T5's, T45's, and 3650 manual transmissions used in Ford Mustangs....have fun!!


Thanks!

So this puppy can drive a standard VW gas tach with no calibration?

I'd rather measure the real RPM then read "a rpm" that comes from the alternator.


The alt. could slip and all sorts of stuff. Jimbotes method is the superior for sure. Mine is just dirt cheap. :wink:
Title: Re: inductive pickup part number.....
Post by: jimbote on December 05, 2008, 06:58:54 pm
Quote from: "Smokey Eddy"
Quote from: "saurkraut"
Quote from: "jimbote"
OK....at the behest of others interested....here is the part number of the Ford inductive pickup I used for my tacho conversion........................... XR3Z-7H103AB ....retails for $23.90 stateside....as far as I know this pickup can be found on all 99' and newer T5's, T45's, and 3650 manual transmissions used in Ford Mustangs....have fun!!


Thanks!

So this puppy can drive a standard VW gas tach with no calibration?

I'd rather measure the real RPM then read "a rpm" that comes from the alternator.


The alt. could slip and all sorts of stuff. Jimbotes method is the superior for sure. Mine is just dirt cheap. :wink:


Yep...my next one will be the nastiest most dirt cheap conversion on the planet!!!....super rat rod  InVolvo 122s wagon!!!.....dirt cheap rules!! 8)
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on December 05, 2008, 07:16:00 pm
Quote from: "Smokey Eddy"
Well that's the thing vince.

Latches will do, but only to an extent right. A micro controller would be "perfect" but latches would be a good guess.  haha ... so ... when i get it going and it says im idling at 200 rpm i'll know it won't work :P  but if its like 50rpm out i won't care.


Curious as to what a "latch" is....I'm pretty electronics ignorant (would almost like to stay that way) sounds like it may be something that divides the signal?.... :?
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Smokey Eddy on December 06, 2008, 03:56:23 pm
Can be used for many many many many things.

A signal divider is one of them. Each latch can divide a signal by two, so wire a few in series and there you go.
http://en.wikipedia.org/wiki/Flip-flop_(electronics)


^^^
why that isn't a link i have no idea...



Edit: ahh thanks Andrew
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on December 07, 2008, 07:53:47 am
using smokey eddies idea of a latch may work with the inductive crank position sensor already installed in the block of  1Z/AHU/ALH blocks....they read a wheel with four slots so they give four pulses per rev. if you used a "latch" (not sure how they wire in) which divides by two you would get the two pulses needed to drive the tach?....maybe eddie will chime in....
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Vincent Waldon on December 07, 2008, 01:21:36 pm
Yup... you got it... a latch (at least the way Eddie's usin' 'em) divides by two.  Put two of them in a row and you get divide by 4, etc etc etc.

So perfect for what you're thinking.

Not so hot when you need to divide by something other than an exact multiple of two... which is why boxes like the Dakota Digital use a microprocessor to do the math.

Eddie: I'll re-do the calculations sometime soon (gotta head out the door)... the "7.456" was just a random number to make a point that it's not an exact multiple of two... but as discussed recalibrating the tach will likely compensate just fine.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Smokey Eddy on December 07, 2008, 03:49:02 pm
Quote from: "Vincent Waldon"
Yup... you got it... a latch (at least the way Eddie's usin' 'em) divides by two.  Put two of them in a row and you get divide by 4, etc etc etc.

So perfect for what you're thinking.

Not so hot when you need to divide by something other than an exact multiple of two... which is why boxes like the Dakota Digital use a microprocessor to do the math.

Eddie: I'll re-do the calculations sometime soon (gotta head out the door)... the "7.456" was just a random number to make a point that it's not an exact multiple of two... but as discussed recalibrating the tach will likely compensate just fine.



Ahh Genius!
I'm thinking of making a microcontroller later on. Making the flip flop was kinda fun  :D
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Smokey Eddy on December 07, 2008, 03:51:48 pm
Quote from: "jimbote"
using smokey eddies idea of a latch may work with the inductive crank position sensor already installed in the block of  1Z/AHU/ALH blocks....they read a wheel with four slots so they give four pulses per rev. if you used a "latch" (not sure how they wire in) which divides by two you would get the two pulses needed to drive the tach?....maybe eddie will chime in....


I'll post pics of the latches on my other test thread and try and explain how they work. Just trying to make my wiring on the bread board a little more .. visually pleasing. Vince would have my head if he saw crossed wires and other such electronics blaspheme.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Rabbit TD on January 14, 2009, 11:28:24 pm
Quote from: "jimbote"
Okydokes,

The Ford probe (with no voltage applied) can drive the VW 4 cylinder gas engine tach and produce an accurate RPM if it sees two chunks of steel every rotation of the crank shaft.

True or no

does the Ford probe have only two wires (signal and ground)?


True.....the ford probe and "most" magnetic inductive sensors (found in automotive applications) have only two wires that are interchangeable signal or ground as in it does not matter which wire goes to ground and which wire goes to signal....the two leads or pins in "most" sensors are only the termination of a coil of copper windings around a magnet....now all "inductive" sensors do not have a "magnet" some are merely a coil of windings around a laminated core and the moving poles are magnets ie the magneto on a lawn mower.....but for this application it would probably be easiest to source and use a "magnetic inductive" pickup ....being as how it can be difficult to attach magnets to the crank pulley....[/quote]


I really like this method of driving a tach.  I was looking at one where somebody put an optical pickup sensor in the timing belt cover and it read off the pump sprocket but this seems beter to me and even less complicated.  I guess the ford probe will work with other tachometers besides VW too won't it {please say yes}.  I just got a mig welder for Christmas and this will probably be my first project :D
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on January 15, 2009, 03:43:20 pm
Quote from: "Rabbit TD"
Quote from: "jimbote"
Okydokes,

The Ford probe (with no voltage applied) can drive the VW 4 cylinder gas engine tach and produce an accurate RPM if it sees two chunks of steel every rotation of the crank shaft.

True or no

does the Ford probe have only two wires (signal and ground)?


True.....the ford probe and "most" magnetic inductive sensors (found in automotive applications) have only two wires that are interchangeable signal or ground as in it does not matter which wire goes to ground and which wire goes to signal....the two leads or pins in "most" sensors are only the termination of a coil of copper windings around a magnet....now all "inductive" sensors do not have a "magnet" some are merely a coil of windings around a laminated core and the moving poles are magnets ie the magneto on a lawn mower.....but for this application it would probably be easiest to source and use a "magnetic inductive" pickup ....being as how it can be difficult to attach magnets to the crank pulley....



I really like this method of driving a tach.  I was looking at one where somebody put an optical pickup sensor in the timing belt cover and it read off the pump sprocket but this seems beter to me and even less complicated.  I guess the ford probe will work with other tachometers besides VW too won't it {please say yes}.  I just got a mig welder for Christmas and this will probably be my first project :D[/quote]

the answer would be yes!!....We (my pop and I) did some testing on an old ford ranger tach also and it worked just as well....good luck!!! :D  :D
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimfoo on January 17, 2009, 12:18:55 am
I noticed the Dodge at work has an interesting pickup. It is a coil in the middle of an m shaped piece of steel. It is just clamped on the outside of the alternator with a very large hose clamp, over the windings.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on February 25, 2009, 09:10:04 am
Just wondering if anyone else has tried my "ford inductive" tach driver method.....also wanted to report I have put over 2k miles on this mod and its working flawlessly still....please let me know what successes/failures you have had :D
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: westcoaster on March 04, 2009, 12:14:14 am
I'll let you know how this works in my suzuki samurai....

It's real, it's cheap, and it's simple.
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: BGA on March 28, 2009, 05:25:12 am
Wonderful thread. I have nearly finished my mTDI AFN-based build. For monthts my brain has worked on the problem: how to use the nicely built in vw sensor. Biased more to mechanics than electronics I knew that filling two gaps on the sensorwheel with steel would do the job. Not nice work wih an assembled engine! I knew that a divider by two would do the jobb. This and a device to protect it from spikes is all I knew on the electronicall side of it, so now I look forward to Smokey Eddys solution. The vw sensor (G28) has three terminals.1 and 2 is the coil and I guess 3 is grounding the capsule. I connected 1 and 2 to a volvo/yazaki gasser tacho and tested it on my lathe and it showed correct and stabel rpm.


Bo Gunnar
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on March 31, 2009, 09:02:46 am
Quote from: "BGA"
Wonderful thread. I have nearly finished my mTDI AFN-based build. For monthts my brain has worked on the problem: how to use the nicely built in vw sensor. Biased more to mechanics than electronics I knew that filling two gaps on the sensorwheel with steel would do the job. Not nice work wih an assembled engine! I knew that a divider by two would do the jobb. This and a device to protect it from spikes is all I knew on the electronicall side of it, so now I look forward to Smokey Eddys solution. The vw sensor (G28) has three terminals.1 and 2 is the coil and I guess 3 is grounding the capsule. I connected 1 and 2 to a volvo/yazaki gasser tacho and tested it on my lathe and it showed correct and stabel rpm.


Bo Gunnar


Sweet!!!....cant wait to see the final result... :D
Title: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on March 31, 2009, 09:10:20 am
still working perfectly!!!!
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: regcheeseman on June 01, 2009, 10:06:22 am
so is mine!
 :P

I tried the 'latch' method as the first way to crack this problem. I believe the ratio using UK spec pulleys was close enough 1:10 - the rest could be dialled in with the cal pot.

I used a 'divide by 10' 4017 chip, circuit worked fine on the lab bench. However the W term was too noisy.

I could have used some signal processing on the front end and further signal conditioning on the output to get a decent 12v square wave out.

As for the auxillery pick up method  - it's not factory - adds engine bay clutter and wasn't the reason for this post. Might be nice to tap the bell housing and pickup on the flywheel. Could also work as TDC detection...
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: lord_verminaard on June 02, 2009, 10:04:42 am
still working perfectly!!!!

Good to know!  I have a question- since you are using two nuts 180 degrees out on the crank, it would be feasible then if you were driving the tach with the intermediate shaft or camshaft pulley that you would use 4 "pickups" instead of two, since it turns at half the speed?

Brendan

Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on June 06, 2009, 04:20:19 pm
still working perfectly!!!!

Good to know!  I have a question- since you are using two nuts 180 degrees out on the crank, it would be feasible then if you were driving the tach with the intermediate shaft or camshaft pulley that you would use 4 "pickups" instead of two, since it turns at half the speed?

Brendan



Yes Brendan you would need four (4) "poles" for any shaft running half speed of the crank for and accurate tach signal....Jimmy
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: 92EcoDiesel Jetta on August 02, 2009, 10:23:39 am
Hi jimbote, I just got  CE1 gasoline cluster with a tach which has a fuel gauge on the bottom. I will try to make it fit it my cluster which is a CE2. Looks like I have to custom wire the tach which has a 4 pin connector(only 3 pins used). Did you wire the tach to the voltage stabilizer or direct to 12V ?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: lusob on August 04, 2009, 03:40:26 pm
Anybody have idea how to install tacho from golf 2 GTI with MFA to golf 2 diesel?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Elwood on September 04, 2009, 04:45:48 pm
Really? I can only see the last two of circuit boards. I imagine there should be a wiring diagram?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Elwood on September 05, 2009, 10:40:35 am
what? why are you being indirect?

The original post talks about wiring, and has gaps in it where I believe images should be. I quote the post, and can see the image links for the missing images, but they do not load. Therefore, there should be more images in the original post, most likely wiring diagrams!

All I'm asking is for someone who has them load to rehost them on another website so I can wire up my speedo! Why are you being so difficult?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: regcheeseman on September 15, 2009, 06:49:34 am
Didn't realise they were missing, I'm guessing the IT fascists at my previous workplace have cleared the stash of files that I'd hidden on one of their servers  ;D

Send me your email address on PM and I'll send direct. I'm not in a position to rehost for a few days as my homehub has gone tats up. As soon as I do, I'll change the links in the original post
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: clyde on September 17, 2009, 01:06:54 am

I'd like to see schematics of the VDO tach. Particularly if you have one for the GLI single-plug cluster with MFA. Years 1988 through 1992/

Seems a lot cleaner to change a few electronic parts on a circuit board than to make mods and fasten sensors IF the signal from the W terminal will drive a modified gas tach!
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: regcheeseman on September 17, 2009, 09:23:32 am
Quote
IF the signal from the W terminal will drive a modified gas tach!

No 'IF' about it - no body has bothered doing it for your mk2 set of clocks for the obvious reason that you can buy a mk2 with a diesel tacho (i.e. GL, GTD and GT models) why would you bother converting a set????
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: regcheeseman on September 17, 2009, 09:39:15 am
Pics now back on - cannot find biobill.pcb which is an annoted view of westmoreland pcb with yellow highlighted tracks and component IDs.

Biobill can you help?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: lord_verminaard on September 17, 2009, 12:26:30 pm
Quote
IF the signal from the W terminal will drive a modified gas tach!

No 'IF' about it - no body has bothered doing it for your mk2 set of clocks for the obvious reason that you can buy a mk2 with a diesel tacho (i.e. GL, GTD and GT models) why would you bother converting a set????

Cause finding a CE1 Diesel Tach cluster is next to impossible in the 'States.  :P

Brendan
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Powered by Spearco on October 05, 2009, 11:27:58 am
Help!
Need the sensor decsribed here in this post from the Mustang.
Local parts house's don't have any and was told there on national back order  :-\.
Anyone?

Thanks.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: macka on October 05, 2009, 07:19:50 pm
Help!
Need the sensor decsribed here in this post from the Mustang.
Local parts house's don't have any and was told there on national back order  :-\.
Anyone?

Thanks.

I have a friend at ford in Thunder Bay ON, she said they had none in stock, and the CAT computer showed none in Canada at the dealerships either. She suggested trying to cross reference it with jaguar, or volvo. They used some of the same trannies and sending units.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Powered by Spearco on October 06, 2009, 12:16:22 pm
So now make that an international back-order  :-[.
I'll look back through the posts and see if anyone was able to make the VW crank sensor/RPM sensor work. If I remember right, it needed to be pwr'ed before it would work, but might not be the right amount of volts to work?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: ToddA1 on November 12, 2009, 01:28:57 pm
Question....  I'm working with a gas tach from a '83 Westy GTI.

I'm in the middle of soldering this up and have a question about RV1.  

RV1 has 3 legs.  2 are on the same side and there's one odd, on the oposing side.  When soldering the 22K resistor to the circuit board, am I ignoring the odd leg?  Looking at the back of the board, it doesn't seem to lead anywhere.

Also, what's the benefit of the 3.3uf cap across the needle wires, if it's not critical?

***Edit*** just got back from overpaying at Radio Shack.  Now, they didn't have the 3.3uf, but the (seemingly knowledgeable?) employee told me that a 4.7uf would be very close.  Should I continue searching for a 3.3uf?

-Todd
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: lord_verminaard on December 15, 2009, 08:43:00 am
Hmm, that's a lot better than using JB-Weld.  ;)  (which I've seen a few people using megasquirt on gassers do)

Nice work!

Brendan
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on December 24, 2009, 09:14:20 am
Thanks.  I pulled the sensor out yesterday and realized that I had placed the ring magnets on oriented so that their polarities are repulsing the polarity of the sensor.  I'm going to have to pull them back off, countersink the other side of each and reinstall.  Not a big deal, but I thought I'd mention it as something to watch out for if someone is doing similar.


Nice work...are you still going to shoot the sensor at the edge of the wheel/pulley?....the magnets just may be strong enough to induce an  eddy through the steel of the pulley....let me know how it turns out....and dang I was through flag back in november...I did not even think about looking you up....maybe next trip?....plus I was having mild altitude headache all night at the hotel....Jimmy
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on December 24, 2009, 05:56:42 pm
if any one is interested I may be able to locate a few of the ford speed sensors....I frequent the scrap metal yard and I will keep my eye out....
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Powered by Spearco on December 25, 2009, 12:29:14 am
Yes please. I'd like two if you don't mind.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: ToddA1 on December 25, 2009, 01:42:50 am
I'm clueless about Fords...  where exactly on the transmission would I find this sensor?   The speedometer hole; is it accessible from the engine bay or do I have to get under the car?

1999+ Mustangs and what years of Probes?  Thanks.

-Todd
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on December 25, 2009, 10:49:51 am
Yes please. I'd like two if you don't mind.

I'll see what I can do....
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on December 25, 2009, 10:52:20 am
I'm clueless about Fords...  where exactly on the transmission would I find this sensor?   The speedometer hole; is it accessible from the engine bay or do I have to get under the car?

1999+ Mustangs and what years of Probes?  Thanks.

-Todd

Mustang is a rear drive car....so you will have to get under the car to access/remove the speed sensor....Probes?....probes are front drive...not even sure if they use a similar sensor....
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: ToddA1 on December 25, 2009, 11:53:41 am
Hmmm....  I thought I saw mention of Probes for the sensor.

OK, if I'm under the car, I'm under the assumption it's in the tunnel.  Am I just following a speedometer cable or something? 

Merry Christmas, everyone.

-Todd
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on December 25, 2009, 02:33:02 pm
no cable....but i think it will be on the drivers side output housing....
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: [email protected] on April 02, 2010, 02:44:17 pm
just thought i would add a different PCB to this thread, just in case anyone else comes across it!! i found this in some clocks i had bought to convert

(http://i2.photobucket.com/albums/y17/reactsystems1/album2/tachoboard.jpg)

(http://i2.photobucket.com/albums/y17/reactsystems1/album2/tachoboard2.jpg)

is as standard front and rear...

this is the slightly different circuit :

(http://i2.photobucket.com/albums/y17/reactsystems1/album2/tachocicuit.jpg)

as you can see, all the components that need changing are all there so just follow regcheesemans original modified circuit for what needs changing!

this is the basic lay out drawn by myself lol

(http://i2.photobucket.com/albums/y17/reactsystems1/album2/tachoboarddrawing.jpg)

and this is what mine looked like when finished, i didnt have all the 100% correct components, but made do and it seems to work (reads high @ low RPM i think, OK @ 3K RPM though compared to my mk3 golf tacho)

(http://i2.photobucket.com/albums/y17/reactsystems1/album2/tachoboardmodded.jpg)

hope that makes sense, and helps someone!
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Rabbit on Roids on April 03, 2010, 11:37:43 am
:O what cars came with that fancy MPG gauge? i got one in my MFA, but that would be cooler, or is it just a vacuum gauge?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: [email protected] on April 04, 2010, 10:32:26 am
the clocks are from a mk1 GTi, it has a vac connection on the back (well, a pipe connection anyway!) its just redundant on my clocks (obviously)
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: avocado_tom on July 21, 2010, 01:53:08 pm
Ok, I know this is going to sound a bit daft, but please bear with me.

I would like to build a circuit to convert a VDO tach to use the W terminal (as opposed to using an induction system).  I'm planning on buying a tach off of e-bay or some such.  I know I can use Smokey Eddy's method (and still might) but was wondering how I would use one of the other circuits posted if I wanted to...

I guess my question is: The other circuits appear to be specific to modifying your stock gauge cluster for a tach.  I don't have a stock gauge cluster (this is a conversion project) and therefore don't have the eight connections to the instrument cluster board (labeled 1-8).  I assume, therefore, that those are not something I can use and therefore I should just investigate using the Eddy method?  Or...

Any help in clarifying would be appreciated...
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: crewcabcaddy on August 15, 2010, 01:56:45 pm
And for those of us in not familiar with all the different types/styles of capacitors:

I am in the USA so I first went to Radio Shack and they did not have the appropriate size resistors or capacitors...(small town  :-\).

So did a bunch of web surfing and found Mouser Electronics (http://www.mouser.com/Passive-Components/_/N-5g73/ (http://www.mouser.com/Passive-Components/_/N-5g73/)) to have the best web site and best available stock for small purchasers like me.

Resistors are pretty easy to sort out...I selected 1/2 watt, 1% tolerance, metal film, axial, like you would get at Radio Shack.  I purchased 4 of the lower ohm needed and 4 of the higher ohm needed (I swapped from the tach board where possible so only needed two new resistors per tach conversion).  I purchased 4 of each to work on additional tachometers when/if needed and in case I messed up the first one!

Capacitors seem a bit more difficult to choose, and those more knowledgeable than me should chime in here:
It appeared to me that polypropylene film was the best type for smoothing signal and oscillations.  I chose radial, metalized polypropylene film with the appropriate ratings (0.010 uF aka 10 nF and 0.047 uF aka 47 nF) and appriate space (pitch) between the wires (10 mm for the 0.01 uF and 15 mm for the 0.045 uF).  FYI, the F stands for Farads...the unit of measure for capacitance.  I used 250 volt for the 0.047 uF cap and the only voltage available for the 0.01 uF cap that I chose was 400v.  I kept tolerance below 10%.  the 1431 series (on Mouser's website) worked best for what I thought I needed

I bought 4 each of the two resistors and of the two capacitors and the total with UPS ground shipping was just over $10 U.S.

Hope this helps some of you find the right stuff.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: crewcabcaddy on August 24, 2010, 02:41:23 pm
1996 1Z TDI in MK1 Rabbit:

Made the tach mods and had trouble with the needle not dropping back down to idle RPM...on a whim attached ECU tach signal wire directly to signal terminal on an unmodified tach (with cluster hooked up so it had power and ground already)....and it worked perfectly.

So, if you have this VDO MK1 tach:
(http://soundeco.smugmug.com/Volkswagen/TDI-RabbitPickup/IMGP7067/981231937_rSSxC-M.jpg)

(http://soundeco.smugmug.com/Volkswagen/TDI-RabbitPickup/IMGP7066/981231359_GUfR9-M.jpg)

And you are working with a TDI motor...try hooking the TDI ECU tach output wire directly to the signal terminal...or to slot 5 on your cluster electrical connector.

There are other circuit boards out there for these tachometers, so not sure if it would work for others...but worth a shot before you modify it.
Title: Re: inductive pickup part number.....
Post by: Apsik on October 03, 2010, 07:21:30 pm
OK....at the behest of others interested....here is the part number of the Ford inductive pickup I used for my tacho conversion........................... XR3Z-7H103AB ....retails for $23.90 stateside....as far as I know this pickup can be found on all 99' and newer T5's, T45's, and 3650 manual transmissions used in Ford Mustangs....have fun!!
I have tried your idea but it does not work for me. I have tryed it twice already.
I have imported the sensor from USA.
I have equiped the crank pulley with 2 nuts (180* apart)
I have made the bracket for the sensor.
One wire to the Ground, another to the tacho (red/black wire - terminal 1) and it does not work.
Multimeter detects 0,8Volts when on the "AC Volts" setting. CE1 tachometer rev counter - frozen :-\
I have tested it the 1st time on my 1.9D. It didn't work and I simply bought the diesel tachometer (it is the easiest way in Euope I gues).

Lately I have SWAPed the 3.6 FSI into my friends MK2 Golf and the last thing of the puzzle is to make the CE1 rev counter work. So I have tryed the Ford Sendor Idea again and no luck so far. What am I doing wrong? Any ideas? Or maybe the techometer is differend :-\
The alternator on the 3.6FSI has the W terminal so probably I will buy the Universal Diesel Alternator Tachometer Interface From Dakota Digital to make the rev counter work.
Title: Re: inductive pickup part number.....
Post by: jimbote on November 16, 2010, 07:31:08 am
OK....at the behest of others interested....here is the part number of the Ford inductive pickup I used for my tacho conversion........................... XR3Z-7H103AB ....retails for $23.90 stateside....as far as I know this pickup can be found on all 99' and newer T5's, T45's, and 3650 manual transmissions used in Ford Mustangs....have fun!!
I have tried your idea but it does not work for me. I have tryed it twice already.
I have imported the sensor from USA.
I have equiped the crank pulley with 2 nuts (180* apart)
I have made the bracket for the sensor.
One wire to the Ground, another to the tacho (red/black wire - terminal 1) and it does not work.
Multimeter detects 0,8Volts when on the "AC Volts" setting. CE1 tachometer rev counter - frozen :-\
I have tested it the 1st time on my 1.9D. It didn't work and I simply bought the diesel tachometer (it is the easiest way in Euope I gues).

Lately I have SWAPed the 3.6 FSI into my friends MK2 Golf and the last thing of the puzzle is to make the CE1 rev counter work. So I have tryed the Ford Sendor Idea again and no luck so far. What am I doing wrong? Any ideas? Or maybe the techometer is differend :-\
The alternator on the 3.6FSI has the W terminal so probably I will buy the Universal Diesel Alternator Tachometer Interface From Dakota Digital to make the rev counter work.

power and ground to the tach? ....one lead of inductive pickup to the input "signal" terminal on the tach the other lead of the pickup to good ground....I don't think it has anything to do with the tach...I tested using a ford ranger pickup tachometer....do you have any pictures of your setup? ...how much clearance do you have between the sensor and the nuts?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on November 16, 2010, 07:49:04 am
as far as the wiring very simple....one leg of the sensor goes to the tacho input....one goes to ground....of course you need battery positive and ground to the tach

So the wiring is *four* wires.  Ground for the pickup, the + from the pickup to the tach, ground for the tach AND +12V to the tach.   Do you have the +12V, ground and the signal from the pickup all connected to the tach?

yes four wires that's it....one leg of sensor to ground, one to tacho input.... the tach needs power and ground...simple.....make sure the gap is around .020 between the sensor and "reluctor" nuts
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on November 21, 2010, 04:06:52 pm
just converted over a motor meter cabriolet tachometer for diesel, haven't tested it yet but once i do and know it works i'll post it here
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on November 21, 2010, 10:36:47 pm
this is to convert a cabriolet motometer tachometer into a vw diesel tachometer

board with tracks drawn on to it (i'll add proper parts lables soon):

(http://img.photobucket.com/albums/v306/Trev0rbr/DSCN0721.jpg)

Original diagram i drew to make it easier for me to understand to convert it:

(http://img.photobucket.com/albums/v306/Trev0rbr/DSCN0727.jpg)

and i took my diagram and used to figure out how to make the cabby board match this:

(http://i492.photobucket.com/albums/rr281/regcheeseman/tachomods/final_diesel.jpg)

directions

1. replace d1 with a jumper wire
2. remove r2 and r3
3. replace r1 with a 15k ohm resistor (you can use the original r7 for this)
4. replace r4 with 191 ohm resistor (i used 2 100 ohm in series)
5. replace r7 with 10k ohm resistor
6. replace c1 with a 10nF capacitor
7. replace c2 with a 47nF(.047uF) capacitor
8. replace c3 with a 47uF capacitor (i used electrolytic how ever i just realized that i only removed c3 and the tach still worked when i tested it, so i am going to guess it is only there for filtering because it goes from the signal input to ground, replace it anyway just to be sure)
9. replace c4 with a 3.3uF capacitor (i used 3 10uF capacitors in series)
10.  calibrate!!!! i usually put the pot on the end of a long wire that way i can fully install the cluster and then adjust the tachometer as i drive, and then when i am finished tuck the wire away neatly behind one of the dash blanks
11.  enjoy your accurate fully functioning factory appearing diesel tachometer
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: GEE-BEE on November 22, 2010, 06:13:34 pm
How about a pic of the complete cluster when done on here...

GB
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on November 30, 2010, 12:19:22 am
almost done, i am quite proud of this one, i'll switch pictures once its totally complete

Guys instrument cluster, meister gauge faces, and also will have all blue led light, gonna be something for everyone to droll on, i know i have already.

(http://img.photobucket.com/albums/v306/Trev0rbr/DSCN0738.jpg)


with blue leds on:
(http://img.photobucket.com/albums/v306/Trev0rbr/geebee/DSCN0764.jpg)
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on November 30, 2010, 12:23:18 am
here is the one i have in my jetta coupe, in person it is hard to tell that there is a sticker where it says sucks

(http://img.photobucket.com/albums/v306/Trev0rbr/DSCN0664.jpg)
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: GEE-BEE on December 25, 2010, 07:18:31 pm
Thanx it's perfect

The jetta dash is going in while I go to Japan and Boracay island

Jan 19/ 30

GB
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: regcheeseman on January 07, 2011, 07:38:57 pm
Quote
Guys instrument cluster, meister gauge faces, and also will have all blue led light, gonna be something for everyone to droll on,

If you've done a board mode then the revcounter spacings will be all wrong - it'll never calibrate properly. The diesel tacho should indicate 5500 rpm at full scale deflection.

If anyone wants fully vectorised clock layout files - just ask.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: ToddA1 on February 22, 2011, 05:26:14 am
Has anyone else completed jimbote's method with the Ford VSS?  Something I didn't see mentioned was how far apart the nuts added to the crank pulley need to be.  I'm sure the closer to the center they are, the higher the rpm would read.

-Todd
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: jimbote on March 15, 2011, 05:12:57 pm
Has anyone else completed jimbote's method with the Ford VSS?  Something I didn't see mentioned was how far apart the nuts added to the crank pulley need to be.  I'm sure the closer to the center they are, the higher the rpm would read.

-Todd

Todd...the nuts need to be at the edge of the pulley so they can induce a current in the pickup....it will make no difference in RPM whether they're near the center or on the edge....just two pulses per revolution is all that matters...but they must be positioned so they sweep very closely to the sensor....are you having an issue mounting them at the edge?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: ToddA1 on March 15, 2011, 05:23:21 pm
No issues with mounting them, but I wanted to know before I mounted them....  just in case.

I forgot to order than sensor with my last parts order, but it'll get done.  I want an actual tach signal for my remote starter....  I don't like relying on voltage sensing.

Thanks.

-Todd
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Powered by Spearco on May 22, 2011, 10:43:46 pm
I just wanted to say thanks for the info on the Ford sensor. It works on my Autometer tach.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: srgtlord on August 13, 2013, 10:36:29 pm
I just read through this entire thread and could not find anything that came close to the tach that came out of the 85 gas golf I have...

(http://i692.photobucket.com/albums/vv285/srgtlord/PIC_0065_zps3bb5e6e1.jpg)[/URL

I did however notice the first tach picture has the same number of components. ANy help would be greatly appreciated (http://s692.photobucket.com/user/srgtlord/media/PIC_0065_zps3bb5e6e1.jpg.html)
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on August 15, 2013, 07:25:31 am
most of them have pretty similar schematics, take a picture of the other side of the board so we can see the traces.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: srgtlord on August 15, 2013, 07:55:07 am
Ill take a picture, but I think I figured it out. This has an almost identical set of components to the first VDO gasser tach in the thread. I started tracing components and resistors and there are only 2 resistors that are different, one is 200 ohms and the other is 16 kilo ohms on my board. I do beleive the 16 kilo ohms coincides with  r5 which has a dunno as the resistance label. The 200 ohm coincides with 162.

Ill double check on the capacitors but it looks like they are all the same. Its odd how VW decided to change the two resistors.
I think by following the conversion schematic for the first VDO gauge I should be in the ballpark of a working tach.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on August 15, 2013, 11:57:13 am
basically if you can make what u have match the td circuit that regcheeseman posted then it should work, i've done it before on boards no one had converted, i think i posted one a few pages back
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: srgtlord on August 15, 2013, 12:38:29 pm
Thats exactly what I was thinking :) Looks like Ill be starting in on this tonight 
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: CrAzY_DrIveR on September 16, 2013, 05:17:33 pm
As crewcabcaddy said just conecting the ecu signal directly works pretty well.
Now that this is done can anyone help me with my speedometer conversion? :)

http://www.vwdiesel.net/forum/index.php?topic=33926.msg319201#msg319201

video of the tachometer

http://youtu.be/LWae5V6T1gw

(http://img198.imageshack.us/img198/4231/o80h.jpg) (http://imageshack.us/photo/my-images/198/o80h.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: R.O.R-2.0 on October 20, 2013, 04:12:36 pm
I just read through this entire thread and could not find anything that came close to the tach that came out of the 85 gas golf I have...

(http://i692.photobucket.com/albums/vv285/srgtlord/PIC_0065_zps3bb5e6e1.jpg)[/URL

I did however notice the first tach picture has the same number of components. ANy help would be greatly appreciated
 (http://s692.photobucket.com/user/srgtlord/media/PIC_0065_zps3bb5e6e1.jpg.html)

That dont look like a VDO tach, it looks like a Moto-Meter, and they are 100% different..
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: srgtlord on October 21, 2013, 03:56:43 pm
Well believe it or not..IT WORKS! and yes this is a 1985 gasser VDO tach
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on October 25, 2013, 11:10:48 am
they all look a bit different, but they are all quite similar, and they are all very simple circuits.  it would be quite easy to just build the board yourself if so long as you could find the correct chip.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on October 25, 2013, 11:11:31 am
actually can you confirm all the numbers on that chip????

specifically sn29736p?????
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: srgtlord on October 25, 2013, 12:56:18 pm
Unfortunately the only picture I have is the one I posted and the tach is currently installed in the car at the moment :(  When I go to calibrate the tach Ill pull the tach out of the cluster to get another look at the part number but this probably wont happen until spring.....
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on October 25, 2013, 01:19:23 pm
thats fine, i'd just like to see what it is eventually, i couldn't find a replacement for the 215 chip found in older tachs.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: srgtlord on October 25, 2013, 02:37:40 pm
As a side note I found a picture of a moto-meter tack that has *drumroll please* the chip with the same part number

(http://joaoasduarte.magix.net/public/cgp/diy/rpm/IMG_1227.JPG)
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: DraQuTzU90 on November 20, 2013, 02:39:37 am
this is to convert a cabriolet motometer tachometer into a vw diesel tachometer

board with tracks drawn on to it (i'll add proper parts lables soon):

(http://img.photobucket.com/albums/v306/Trev0rbr/DSCN0721.jpg)

Original diagram i drew to make it easier for me to understand to convert it:

(http://img.photobucket.com/albums/v306/Trev0rbr/DSCN0727.jpg)

and i took my diagram and used to figure out how to make the cabby board match this:

(http://i492.photobucket.com/albums/rr281/regcheeseman/tachomods/final_diesel.jpg)

directions

1. replace d1 with a jumper wire
2. remove r2 and r3
3. replace r1 with a 15k ohm resistor (you can use the original r7 for this)
4. replace r4 with 191 ohm resistor (i used 2 100 ohm in series)
5. replace r7 with 10k ohm resistor
6. replace c1 with a 10nF capacitor
7. replace c2 with a 47nF(.047uF) capacitor
8. replace c3 with a 47uF capacitor (i used electrolytic how ever i just realized that i only removed c3 and the tach still worked when i tested it, so i am going to guess it is only there for filtering because it goes from the signal input to ground, replace it anyway just to be sure)
9. replace c4 with a 3.3uF capacitor (i used 3 10uF capacitors in series)
10.  calibrate!!!! i usually put the pot on the end of a long wire that way i can fully install the cluster and then adjust the tachometer as i drive, and then when i am finished tuck the wire away neatly behind one of the dash blanks
11.  enjoy your accurate fully functioning factory appearing diesel tachometer

Hello, I'm trying to build a board from 0 with sn29736p chip like yours with the diagram that you posted earlyer but it doesnt work, please can you post here your final diagram? maybe i dont do something right. It's the second time i try to build that board and still doesnt work.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on November 27, 2013, 02:25:58 pm
what u see is what i did, and it did work, have you tried replacing the caps again??  have you played with the potentiometer?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: 8v-of-fury! on January 16, 2014, 12:20:12 am
Interesting to see that you-tube video up there of the ECU perfectly running the older style tach. One day, maybe when I do an E-TDI swap.. this will be beneficial ;)
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: TimpanogosSlim on September 19, 2014, 11:22:31 pm
Just did this mod to an 83 jetta gasser tach i pulled out of the junkyard today. Went pretty well. Had to tack the 10nf to the back of the board because what i had was 7mm spaced trimmed leads.

Had to parallel a 390 and a 360 to get to 191-ish ohms. Sorted and tested until i had 189.6 ohms so within 1%, should be fine.

'course the car isn't running yet, so . . . .
 
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: TimpanogosSlim on September 29, 2014, 11:35:10 pm
In case anyone was reading - my bentley manual says that the W terminal should connect to C11 on the fuse/relay panel in 83/84 rabbit/jetta diesel what came with the tach from the factory.

Has anyone tried this?

I have a thing about doing things the right way when i have some clue what that way is. So I'd like to try it. If it's likely to work.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: TimpanogosSlim on November 04, 2014, 01:35:07 am
FWW, although my wire harness already plugs into the W terminal (probably for the "shift up you dummy!" light in the cluster), my modified tach isn't moving.

since i got it at a junk yard, I have no way of knowing whether it worked before i modified it.

EDIT: It does work, intermittently. I have reason to believe that it's really my alternator that is intermittent, unfortunately.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: srgtlord on November 10, 2014, 08:53:48 am
I wonder If you have a loose connection somewhere. It might be beneficial to run a lead from your tach to the alternator w terminal
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Kraftwerk on November 14, 2014, 05:05:28 am
So, I have a CE1 (2 connectors) VDO gasser tach out of, I think, '86 Jetta, and I'd like to try to make it work in my '87 Passat diesel.
Diesel tachs are impossible to find, and since this one is going to spin a little higher, 5k tach wouldn't do it anyway.

So, anyone knows what should I do to this, which schematics work, etc? I have a friend who is an electrical engineer, but I have to give him something to start with...

http[TACH IMAGE]://[REMOVE THIS]s26.postimg.org/c84i1wbi0/IMG_20141113_200330.jpg
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: libbydiesel on November 26, 2014, 07:04:31 pm
Here's the missing pic from the first post.

(http://i13.photobucket.com/albums/a269/libbybapa/tach_zps5d06c6cb.jpg)

In the text following the pic I'm not sure what the "zener" is, the pic doesn't show a C2.  Is it the white component bottom left?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on November 28, 2014, 12:40:59 pm
c2 i would also guess i the large white compnent on the left.  the zener must mean a zener diode, which i would guess is the component at the bottom right, since its the only thing that looks like a diode.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: libbydiesel on November 28, 2014, 01:00:07 pm
After posting I realized that board is the exact same as the one you posted in reply 100 and quoted by DraQuTzU90 above.  Your pic shows that C2 is the white capacitor.  I also agree that the 'zener' is the D1 diode in the bottom right. 
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: RabbitJockey on November 28, 2014, 01:07:16 pm
After posting I realized that board is the exact same as the one you posted in reply 100 and quoted by DraQuTzU90 above.  Your pic shows that C2 is the white capacitor.  I also agree that the 'zener' is the D1 diode in the bottom right.

looks like it's even labeled as a z on that board.  and what ever i wrote for that boards instructions definitely worked, looks like someone else had already figured it out, but i couldn't see the picture so ended up writing my own up.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: TimpanogosSlim on December 18, 2014, 02:43:52 am
I am pleased to report that, having replaced the original voltage stabilizer in my 1983 jetta gasser cluster with an $0.75 Fairchild LM7810, my tach works excellently! No wiring mods at all in my 1984 jetta. I modified the tach board and nothing else.

I'm sure i still need to tweak it, which will happen after i fasten a piezo pickup to my #1 injector line and hook up a silly scope.

PM me if you need to replace your voltage stabilizer. The $28 charged by mk1autohaus is highway robbery. $5 CONUS shipped. You'll need a stack of 7 or 8 #4 brass washers and a #4 1/2" wood screw because the LM7810 mounts up-side-down vs. how the original part was mounted. I have exactly 3 extras. heck, I'll even throw in a brass #4 1/2" screw .
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Kraftwerk on January 01, 2015, 09:42:06 am
Care to explain?

You modified the board as per original instructions AND replaced voltage stabilizer, OR just replaced voltage stabilizer and that made it work?

Sorry and thanks.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Kraftwerk on January 17, 2015, 12:00:30 pm
How do I take this apart without breaking anything?

Pic 1 (https://www.dropbox.com/s/hxeqxg4qm8kmjpz/CAM00798.jpg?dl=0)
Pic 2 (https://www.dropbox.com/s/0w2wv73hvhs35on/CAM00799.jpg?dl=0)
Pic 3 (https://www.dropbox.com/s/vjtpuo0ervevjpp/CAM00800.jpg?dl=0)
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Kraftwerk on January 31, 2015, 08:24:44 am
Huh?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: libbydiesel on February 05, 2015, 10:11:26 am
If you are stuck there, I question whether or not you should be attempting the conversion. 

De-solder the two wires noting their color/location.  Lift off the circuit board.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: trellsbells2 on March 13, 2015, 12:46:13 pm
Has anybody modified this board to make it work? the circuit is different, but not too much different than the other boards mentioned in this post. Still cant figure out how to covert it though. I have a schematic drawn out if anyone wants to see that but it isn't the prettiest drawing :)
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: libbydiesel on September 06, 2015, 06:07:31 pm
I just got a mk1 tach swapped over in my '79 rabbit.  Along with replacing the appropriate tachometer components I also had to add the W-terminal to the alt also as the alt didn't have one.  It works great. 
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: hugoalves6 on September 01, 2017, 08:55:11 pm
Guys any one have the complete guide with pictures, I have and M-TDI, and need to put the petrol rpm gauge in my cluster but ive been told that is needed to change somethings to make it work with the w terminal, and them i was sent here to this post, any help please?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: libbydiesel on September 01, 2017, 09:39:30 pm
Botophucket strikes again...

This should help.  https://www.thesamba.com/vw/forum/viewtopic.php?t=610274&highlight=diesel+tachometer
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: protofuria on February 09, 2018, 03:55:57 pm
Hi guys!

I know this topic is old and probably dead, but I'm trying to put a MK1 gti cluster into my '86 diesel caddy. Most pictures here have disapeared (thx photobucket!)

anyone could help me with it? here's a picture of my circuit board :

(http://nsa39.casimages.com/img/2018/02/09/mini_180209103140747606.jpg)

(http://nsa39.casimages.com/img/2018/02/09/180209095820606182.jpg)
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: libbydiesel on February 09, 2018, 06:31:11 pm
http://www.vwwatercooled.com.au/forums/f28/how-tachofy-your-mk-1-diesel-31515.html

You'll have to trace out your board (front and back) but they are all basically the same schematic and require the same replacement items. 
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: regcheeseman on February 15, 2018, 06:39:20 pm
Can't believe this thread is still running, only popped in to borrow the pic links but thought they may have been ruined by photobucket.

Use chrome browser and apply the photobucket fix and all the pictures reappear - if anyone does want the originals please email me regcheeseman AT btinternet DOT com
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: InSaneVw on April 29, 2018, 12:18:34 pm
83 Rabbit LS with a 1.6TD

I was wondering if anyone has come across the tach needle not moving at all when done the conversion?  I have followed the board changes, got confirmation that I have 8v AC from the W terminal.

Traced the line from the Alternator to pin #5 on the 18 pin connector that plugs into the cluster and have continuity thru said line. Traced the pin# 5 on the back of the circuit sheet which goes to what I'm 99% sure is the Signal post on the tach circuit board. ( I used the 83 GTI circuit sheet ) ** Is this my mistake? ** looking at them all I see is that the 2 circuits that went to the clock back were cut at the factory on the GTI one.

The cluster has power ( lights, fuel and temp gauges work ). Next step is to take apart and triple check my circuit board work.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: srgtlord on April 30, 2018, 10:11:37 pm
Silly question but did you run a line from the W terminal on your alternator to the signal input on the cluster?
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: InSaneVw on May 04, 2018, 12:30:15 am
Yes ran a line from the 'W" terminal to the non used pin#5 line which is the tach signal. confirmed voltage and continuity all the way up to the cluster. Might be the voltage/tach stabilizer guess ill have to meter that as the needle does not move at all. Just curious if everyone keeps there stock circuit sheet or use the GTI one.
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: Andrei HZX on November 26, 2018, 04:42:52 pm
Hello . I have a vw golf 2 1.6 TD . Recently I bought a tachometer from golf 3 1.9 td or tdi . I have installed and modified the speed cable for speed sensor and the rpm from alternator battery. Now the problem is the tachometer is standing the rpm to 5000 max when ai start the car . How can I resolve the issue to return to normal . Help me !
Title: Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
Post by: ORCoaster on November 26, 2018, 10:36:36 pm
Do you need to modify the electronics on the board?  Or is that only apply to a gasser to diesel conversion?