Author Topic: Gas Tacho / Revcounter Conversion to Diesel W terminal  (Read 169475 times)

Reply #120October 25, 2013, 01:19:23 pm

RabbitJockey

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #120 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.
98 Pontiac Grand Prix GT:stock daily
 81 Jetta: in progress 1.6td, ported head, holset turbo.
81 Rabbit:AAZ, hybrid T3 turbo, Giles pump, lightened fw, and yellow clutchnet clutch.

Reply #121October 25, 2013, 02:37:40 pm

srgtlord

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #121 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


Reply #122November 20, 2013, 02:39:37 am

DraQuTzU90

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #122 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):



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



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



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.

Reply #123November 27, 2013, 02:25:58 pm

RabbitJockey

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #123 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?
98 Pontiac Grand Prix GT:stock daily
 81 Jetta: in progress 1.6td, ported head, holset turbo.
81 Rabbit:AAZ, hybrid T3 turbo, Giles pump, lightened fw, and yellow clutchnet clutch.

Reply #124January 16, 2014, 12:20:12 am

8v-of-fury!

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #124 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 ;)

Reply #125September 19, 2014, 11:22:31 pm

TimpanogosSlim

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #125 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 . . . .
 

Reply #126September 29, 2014, 11:35:10 pm

TimpanogosSlim

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #126 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.

Reply #127November 04, 2014, 01:35:07 am

TimpanogosSlim

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #127 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.
« Last Edit: November 07, 2014, 11:48:13 pm by TimpanogosSlim »

Reply #128November 10, 2014, 08:53:48 am

srgtlord

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #128 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

Reply #129November 14, 2014, 05:05:28 am

Kraftwerk

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #129 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
D24TIC power!

Reply #130November 26, 2014, 07:04:31 pm

libbydiesel

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #130 on: November 26, 2014, 07:04:31 pm »
Here's the missing pic from the first post.



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?

Reply #131November 28, 2014, 12:40:59 pm

RabbitJockey

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #131 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.
98 Pontiac Grand Prix GT:stock daily
 81 Jetta: in progress 1.6td, ported head, holset turbo.
81 Rabbit:AAZ, hybrid T3 turbo, Giles pump, lightened fw, and yellow clutchnet clutch.

Reply #132November 28, 2014, 01:00:07 pm

libbydiesel

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #132 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. 

Reply #133November 28, 2014, 01:07:16 pm

RabbitJockey

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #133 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.
98 Pontiac Grand Prix GT:stock daily
 81 Jetta: in progress 1.6td, ported head, holset turbo.
81 Rabbit:AAZ, hybrid T3 turbo, Giles pump, lightened fw, and yellow clutchnet clutch.

Reply #134December 18, 2014, 02:43:52 am

TimpanogosSlim

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Re: Gas Tacho / Revcounter Conversion to Diesel W terminal
« Reply #134 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 .