Tachometer low & speedometer high
 

3rd gen, '93.

Everything all OK over the past few years. Then car off the road for approx 2 months (I was out of town). On returning and starting the car, neither the speedometer or the tachometer worked (both at zero). Tried disconnecting and reconnecting the battery but did not fix. Fuses OK. Wiring not been touched or changed since car was last on road.

Bought a used (but believed OK) center control panel and replaced the old one. On start-up and driving, both meters seemed OK (no longer at zero). Car ran OK but I didn't check if the tacho and speedo were accurate at that point. However after a few miles both meters started moving up and down suddenly and seemingly independently, despite constant engine RPM and car speed. A few minutes later, both meters went down to zero and stayed there.

Stopped car, turned ignition off then restarted and drove the car. Both meters still at zero. Stopped, the car, disconnected battery, waited a while for engine/engine compartment to cool down a little, reconnected the battery and started and drove the car. Now both meters are "working" but Tacho. is too low (approx 50% low) and speedo. is too high, (approx 60% too high).

Tacho. appears to run non-linear with actual RPM (accurate at idle but flattens off significantly above 2000-3000-RPM) Speedo. seems linear with car speed but reading is much too high - gives reading of 110 MPH at actual car speed of approx. 75 MPH

Any ideas anybody?

Thanks

Dave

Further problems with my 3rd gen '93 Speedometer and Tachometer
 

Ref my last post, I never was able to find the problem. However, now it has changed and the speedometer now registers proportional to the engine speed when the car is stationary and not in gear!! Weird. Anyone else ever seen this?