tachometer installation issues

[72ghiavert]

I know that installing a tach should be a traight forward installation, but this is what is going on.

I connected:
black to ground
green to the negative on the ignition
red to fuse number 7 on a 72 fuse box
white to the white cable that goes to the headlights from the fuse box

I turn on the switch to start the car and the oil/gen lights are off. disconnect the tach power cable (red wire) and lights come on, first time I have seen this out of the few times I connected tachs. any ideas?

[FJCamper]

Hi 72Ghiavert,

What brand and model of tach?

Is it off another VW where you saw it work? Here's a tip from SunPro:


1. Clip the BLACK lead from the tachometer to
the negative (-) battery terminal.
2. Clip the RED lead from the tachometer to the
positive (+) battery terminal.
3. Clip the GREEN lead from the tachometer to
the negative (-) side of the ignition coil or tach
signal connection point as indicated in the
ELECTRICAL CONNECTIONS section of this
manual. Do not allow this connection to
touch ground!
4. The WHITE lead is for instrument panel
lighting, and need not be connected for this
check.
5. When all connections are secure, start the
vehicle’s engine. Confirm the operation of the
tachometer throughout the operating
temperature range of the engine, and at both
curb idle, and higher engine speeds. The
tachometer should follow the speed of the
engine smoothly, and show no signs of erratic
operation.

[72ghiavert]

It is an autometer with shifting light. It it a used one that somebody gave me. I will perform those checks today and post back the results.

[72ghiavert]

Thanks for your recommendations.

Well, testing was done, the tach works fine. I went ahead and traced all the cables I worked with last night. In the process I noticed tha the oil sender was faulty (leaking a little oil from the center of it) and replaced it. Reconnected all the cables back including the tach ones and now it is working fine.

At idle.


With a little bit of gas.
.

[69satellite]

I got the same tach laying in my shed. So what did you end up doin wiring wise? I think I will mount mine down low