Do you need to modify the electronics on the board? Or is that only apply to a gasser to diesel conversion?
Went to Car Lab and could not find this tach anywhere. I wonder if it is a gasser and not for a diesel.
Hi Mr RabbitJockey, thank you for your time and effort, By following your guide I got the Tach to work on my AAZ pickup installation, I used the resistors I had, and although not horrible off it is working only need to do the cal now.
Cheers
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
I use this all the time. I try to find those old clusters on CL and convert them to work with a diesel. I think I still have two to do. Not a real big priority but If I just want to goof off at the workbench they are there calling my name.
hello i am glad to hear it, I can't believe how long its been since I did that conversion. I used to convert them and sell them but I never charged enough to make it worthwhile. Now i think it's easier and cheaper to just add the glowplug led and then use a dakota digital adapter with the unmodified gas tach. But for a DIY person at home with some soldering skills converting the tach yourself is a great option and only costs a few pennies and your time.
My take is that you end up with a VDO/ VW factory-looking unit when you are done. Toss that clock outta there. You probably have a digital one on the radio or phone display anyway.