schlag

Once upon a time my tach worked fine.

Then we re-sealed the front of the engine, did some other work etc. and the car was down for several months without being driven.

The battery died, so to test it we had to jump it a few times.

The tach doesn't work now, but oddly enough the "upshift" light comes on at a certain RPM and the MPG guage works fine.

Any ideas, suggestions?

SoCal Driver

The tach works off of the same circuit as the coil wire from the DME. Actually splits off the harness at the DME and goes to the instruments. Look for a disconnected wire between them.

Cass944

if i turn my key to the first position so that only the radio is on then roll down my passenger side window, my tach jumps to redline.... hah

iloveporsches

My tach doesn't work until I smack the side of the dash.

Hawk36

Good, I'm not the only one that has to hit the dash to get the tach working. Thought I was going to have to replace it...thinking big bucks....until I hit a bump and the tach came alive. Now I only have to tap to dash in front of the tach every once in a while.

SoCal Driver

You guys scare me. Mine works great.

Zero10

Hrm, mine was dancing for a while, if I kept it at a steady 4 or 5k, it would bounce between 2k and redline, but one I pulled the gauges to change the bulbs, I cleaned up the contacts, and it worked fine. An interesting note, my odometer also did not work until I cleaned the gauges, however the speedometer did work, they are seperately powered? Or perhaps seperately grounded? Potential way to keep the mileage real low on your car.

schlag

I looked at the shop manuals and damn, that's confusing.

Any idea on precise physical locations of wires that might be loose or disconnected?