Tachometer 86 golf

Oh yeah, and I have a friend who's pretty heavy into electronics so if you have any ideas in that respect he might be able to check some things.

Thanks,

-Andrew

My bet is that you have a bad ground connection. The circuit that it is on grounds "under the left hand side of the instrument panel" That's what Bentley says anyway. I'd have to look in my car to be more specific, but it's pretty damn cold out right now. It should be a brown wire.

It could also be a faulty voltage stabilizer. I don't know if those fail often or not. The tach should be getting 10V, but I think you'd have to pull the instrument cluster to test it. I would think that if that failed you would get zero volts, but I can't say for sure.

Or it's just a bad tach...

Is anything else in your dash acting funny (or not working at all)?

Good luck,

Jason

Does your car have an upshift indicator, and if it does, does the upshift indicator work? If you have a working upshift indicator, it would mean that the instrument cluster does get the tach signal.

A friend with an '87 Jetta GLi told me that the oil pressure warning system is prone to fail on that vintage Golf/Jetta. The oil pressure warning system has two oil pressure senders and selects between them based on RPM. I don't know how tightly the oil pressure warning system is integrated with the tachometer, but it is conceivable that your problem lies in the oil pressure warning system rather than in the tach itself.

DruG wrote:

Just the tach appears to be acting funny. It's pretty odd to I mean I'd expect it to just not work at all if one particular thing was broken but it still reads engine speed, albeit in it's own particular way.

-Andrew

There are several things in the instrument cluster that share a power source and ground. The only time I've seen my tach act funny it was because of a really wacky bad battery. In my case, it was so weak it wouldn't start. I can't explain how it affected the tach, but it did. Yours appears to be localized.

Another poster mentions the wire from the coil. This sends a pulsing signal every time the coil fires, so the tach knows the engine speed. This wire is not the problem (unless your coil is misbehaving). You said it acts up in the "on" position without the engine running. It should not be getting a signal from the coil at this point.

It gets 10V from the voltage stabilizer which turns it on. The trouble-shooting for this looks very straightforward in the book, but difficult to describe here. Do you have a Bentley? If not, get one. With an '86 you will need it sooner or later, and it will pay for itself the first time you can fix something yourself rather than take it to a shop.

Jason

I do have a bentley and have looked at the test procedure. I'll check it out. Looks like it might just be some messed up circuitry in the tach though.

Thanks,

-Andrew