'90 940 GLE 16V Auto ~93K Speedo issues

[girlbunny]

1990 940 GLE 16V Auto (approx 93,000 Miles)

I've only had this car a short time, so have only just recently been out in it very early in the morning or during the evening. At this time of day, especially when it's a little damp, the speedometer starts acting crazy. Either flicking around wildly, or flicking wildly then sticking at around 80km p/h even though I'm going under 50. When it sticks around 80, it stays there until the car is put in park and the engine is turned off. I'm not sure if it's one, the other, or both together (park/engine off) that makes it relinquish it's hold.

Driving during the day has absolutely no problems whatsoever. Yesterday I went out for a long drive (had to break in the new rotors/disks on the front) and even though I got home at around dusk, I had no problems.

Any ideas as to what the problem could be? I don't relish the thought of going out at night with the speedometer being so fickle!

Thanks (again) in advance.

Sam

[billofdurham]

The speedos on these cars are electronic and are driven by pulses from a sender unit mounted in the differential housing.

Check the wiring is secure at the sensor and spray the contacts with a little WD40 or similar in case dampness has got in.

Bill.

[lewismug]

Bill is correct. My 740 started doing the same thing a few years back. The wiring going into the speed sensor had bent back and forth so much over time that they were almost completely worn in two. I simply stripped the wires back, soldered them back together and covered them with shrink tubing. Had no other problems at all out of it.

[girlbunny]

Thanks I'll have to get a couple of ramps to safely look under the car, but once I do, I'll try it out and get back to you with how things went

Sam