1991 964 speedo / spoiler issues

[ickyrex]

I am trying to chase down the latest oddity going on with my 1991 c2 automatic.

Speedo works fine at first, then needle bounces and drops completely. The speedo will come back intermittently when hitting bumps. Some times even comes back if I tap on the gauge glass. (kinda like you see in the old WW2 movies in the cockpits)

The spoiler can be raised and lowered manually using the center console switch. The problem started shortly after I had the car washed, high pressure jets on the wheels are probably the culprit. After the carwash, I had the brake warning light for a bit, the one depicting the brake shoes. Then the next day my speedo started acting up. The odometer does not register anything while the car is being driven with this fault.

I have pulled the speedo and checked / cleaned the contacts on the back. Since I have the Automatic, there is a circular set of pins as well as the straight set of 4. No positive results.

Next I guess I will have to pull the LF wheel and look for the ABS sensor to see if something is awry.

My mechanic thinks it might also be a "sender" unit from the transmission, since I have the Automatic, but everything I read tells me that the sender unit is part of the ABS wheel sensor.

Should I worry about "spoiler" safety? If the spoiler is down at 70mph will I get too light in the rear?

Since I drive this car daily I would like it to be perfect, but the car still runs great and other than not knowing how fast I'm going, I'm fine. Hoping for an easy fix this time.