Gas Tachometer Conversion to Diesel W terminal - '87 Vanagon

[orbitald]

Hi, my first post so please forgive any mistakes.

I followed regcheeseman brilliant lead and modified a ’87 Vanagon gasser tachometer to diesel. I know my modified board looks a little hack but all the parts I garnered from an old smashed up monitor I found down on Mission street.








R1 = OK ( 100 ohm )
R2 = OK (I think 82 ohm or 72 ohm is OK)
R3 = Remove
R4 = OK ( 191 ohm )
R5 = Remove
R6 = Replace with 10K ohm
R7 = Replace with 15K ohm
R8 = Remove

D1 = Replace with wire link

C1 = Replace with 10nF (nanoF)
C2 = Replace with 47nF (nanoF)
C3 = OK ( 22uf )
C4 = New 3.3uF (microF) across output terminals (I used a 4.7uF and it worked fine)

Adjust RV1 to middle range



Hope this is some helpful stuff and thanks cheeseman!

Let me know if you find any problems with the drawings / diagrams.

[Hillshy]

welcome orbitald

i did this to on my vanagon too, as mine used to be a thursty gasser, works a treat don't it! it just completes any diesel conversion.

 

[Typrus]

Whoa...
Are most gasser tachs about like that? I dunno if I'll be able to find a Rabbit diesel instrument cluster for the Kart, so I need to keep such options open, ja?

[orbitald]

It’s not too hard to calibrate. I purchased a cheap digital tachometer off ebay (~$24 plus shipping) and took readings off they main crank pulley. There is a small hole in the back of the tach housing that gives access to the potentiometer screw which adjust the range. The biggest trick was getting the needle back to its original position. I think it could be done in about 5min with two people but I did it with myself and it took about 15min.

And I'm not sure about other Vanagon gasser tachometers. I am getting a couple in the mail soon and I'll take a look.

David

[Fredwanagon]

When I saw your post, I started to fit my (around 86 1.6TD tach) in my Diesel Vanagon. Mechanicaly, I had to modify the tach cassing to center the round plate in the vanagon cluster clock hole.

Now phase 2 is to plug fuel gauge, water temp and tach.

Fuel gauge, water temp are easy to figure out. I will extend with a wire  from the circuit bord to the guage. (Can I weld a wire on the circuit bord witout melting it?)

The tach has a four pin connector in the back. 3 are used.
Do you know wich pin is the w signal and wich pins are + and -?

I can post pics if you need to see it.

Thanks

[Vincent Waldon]

Yes you can solder a wire directly to a circuit board trace.. two tips:

- careful with the heat... too much and the trace will delaminate

- most circuit boards have a solder mask... a non-conductive (sometimes clear) coating that needs to be gently scraped off to expose the copper trace below.

[Fredwanagon]

The tach has a four pin connector in the back. 3 are used.
Do someone know wich signal correspond to the letters A,B,C,D and E?
see immage on:
http://www.vwquebec.ca/forum/viewtopic.php?t=47110&highlight=

Thanks

[orbitald]

Hey Fredwanagon,

Look up at the circuit board in my original post (orange board with the green traces) and you can see the pinout on the board:

In = W Signal In
+ = +12VDC positive
NC = No Connection
- =  GND

You can look at the connector to see which pin is missing (NC) to orientate yourself

Good luck,

OrbitalD

[orbitald]

Hey,

I have had problems with this conversion and ended up buying a jetta diesel tach and installing it into my vanagon cluster. Until I have a bunch more time to figure out exactly what is wrong with this circuit I advise folks not to try this.

Best,

D

[Otis2]

You have an AAZ in your Vanagon, right?

I have the same AAZ setup in my van, with the 1.6TD diesel tach in the '85 Vanagon cluster. (It says "2,22" on the tach face, right?)

I'm curious how you calibrate your tach to fit with the signal from the alternator on the AAZ engine.  

Mine was way off, far overreading.  I had to replace one of the resistors to get it to read accurately.

http://www.vwdiesel.net/phpBB/viewtopic.php?t=12589

[regcheeseman]

All looks fine but the chip.

can you swap in a chip from a later instrument. SUch as your jetta tach?

What was wrong in operation anyway?

[kendalwoolf]

I just rewired my 1986 Vanagon tach using the schematic on this post and it works fine with my 1.6 Turbo Diesel, running off the W terminal of the Alt.

Check out pictures of the conversion here: http://picasaweb.google.com/kendalwoolf

[Quantum TD]

Just for schnitz and giggles, has anyone else done this mod, and if so, how is it working out?

I just found a tach cluster out of a 1987 Vanagon at my local Pick and pull for $20. Some goon thought he had 'hid' it in the truck of a Mercedes wagon, but I found it.

Anyway, I wanted to hook up a tach for my dad's vanagon. It was a 1.6NA, but we dropped in a 1.9IDI last summer.

Thanks.

[orbitald]

Well I'm glad someone got it to work consistently. Mine was intermittent and I just got tired of fooling with it so I slapped in a diesel tach. Regcheeseman talks about using a different chip that's probably worth a try. To calibrate it there is a little hole in the back that adjusts the pot on the board. Fairly easy but its not exactly linear.

If anyone else gets this going let us all know.

David (in orbit)

[jf9191]

Does anyone have some left over resistors or transistors they would sell me? I cannot find the 10nf capacitor anywhere and its really frustrating. I thought these parts would be really easy to find.