Porsche 928s Tacho Signal

Bmshearer · Bmshearer's Garage

Hey everyone, new here.
Recently I purchased a 1985 928s automatic. I have no signal going into the tachometer and wanted to check where the tachometer signal is originating from. I have replaced the tachometer and cleaned the connections on the back of the pod. If someone could tell me where the signal originates from I'd appreciate it.

neil30076 · neil30076's Garage

Do you have a wiring diagram, and do you know where the EZF is located? If so, that's where it comes from. Starting at the inst panel its via connector B-2, out on a green wire to J-11 on CE panel, loops out to W-11 on same panel to EZF-16.

garylewa · garylewa's Garage

the signal is from a reed switch attached to the outer housing of the transmission. IIRC, it is a round sensor held down by one screw.....you should be able to see it.

Mrmerlin · 03-29-2015, 06:56 AM

Gary are you talking about the round thing bolted to the rear of the transmission?

Landseer · 03-29-2015, 09:51 AM

That's speedo pickup

Bmshearer · Bmshearer's Garage

Sorry for the extremely late reply, been swamped with school work. Thanks for the replies everyone. I do have a wiring diagram and I see now the trace back from the tachometer to the EZF. My new question is when measuring connection B-2, should i be looking at the voltage or something else? I measured in voltage today and was getting at idle ~12volts, when i depressed the gas peddle the voltage would drop slowly. No life in tachometer still.