Speedometer???

This is a problem I've noticed for a little over a year now. On my 1989 Thunderbird 3.8 V6 (Standard) the speedometer needle sometimes does not work. It will go all the way to the right and remain there. The problem will correct itselt when I either hit a bump or if the driverside door is closed hard enough. A couple times, the mileage on the TRIP METER will increase even when the car is remaining still. It happened once while the car was off.

I've heard it could be a cable or a ground of some sort. I've even heard it could be some type of sensor.

I don't believe this is a major concern being that it's been over a year. However, does anybody have any ideas what this problem might be, and how difficult it might be to correct it??????

sounds like a defect in instrument cluster...we send alot of them out for cracked circuit boards and odometer defects/anomalies...not sure if this would apply to you --do you have full electronic/digital or full analog?

I have a problem with my odometer. Doesn't work at all. stuck on 160,000 or so. I have a '93 t-bird. I don't even know if the speedometer is accurate. Not digital...