Symptoms:

1. Starting about 2 years ago, sometimes I would turn the key to ON, and the row of warning lights would not turn on, but instead the Overdrive arrow would light up dimly and stay lit even after the car was started. Usually clicking the OD switch on the shifter a few times would make the light stay off. Typically after the car warmed up, the warning lights would return to normal function. This problem was worse after the car was sitting around for a long time without being started (sometimes weeks at a time as I only use it for long trips and have a "beater" for driving around town).

2. Starting about a year ago, especially after sitting around for a long time without running, when I turned the ignition key to ON, the speedometer would jump to 45mph and sit there, even without the car running. Driving the car a few miles would usually return to speedometer to normal function. During this time, the odometer would behave normally.

3. Starting about six months ago, the odometer would intermittantly stop working, even though the speedometer was functioning normally. During this time period, symptoms (1) and (2) would still occasionally occur.

4. Starting about three months ago, the Odometer stopped working completely, though the speedometer would usually work fine after a few minutes warmup.

5. Starting two days ago, both the speedometer and odometer were dead. I drove the car 700 miles over two days and the speedometer never registered anything except zero. The car was parked for eight weeks before I took it on the long drive yesterday.


I went through the FAQ and it said to check connections at the back of the speedo, grounding at the right passenger footwell, and the sensor on the differential. I tugged on all the speedo connections, couldn't figure out where the grounding is at the right passenger footwell, and wasn't sure about the rear differential sensor. If that was bad, wouldn't I get a fault code from the ABS? My ABS is working fine. The only wires I found on the differential were wrapped in a rubber insulating cover and I think I'd have to cut through that to examine the wires. I decided to post here before I do it and see if there is any more wisedom out there.

Of note: When I turn the key to on, the speedometer jumps quickly to 10mph and drifts down over the course of one second, which I remember as being normal behavior. Also, this speedometer unit is identical to the ones in the later 93-95 940 models, it isn't the older 740 "square" unit.

I suspect a grounding problem somewhere, but I can't find anything that is definitely a ground wire. Are the ground wires solid black? Also, this newfangled 940 type dash isn't giving me many clues as to how to remove the facia cover to get the speedo unit out. On the older 740, it was easy, but now I seem to have two little slots on the plastic cover. Do I shove something in there to get the plastic cover off? I'm clueless about how to remove the thing and don't want to do my usual "break it the first time, do it right second time" method of removal. (EDIT: nevermind, I found removal in the FAQ). I still have all problems though)