Is your Volvo 940 speedometer not working correctly? Here are some problems to investigate that may help you diagnose and fix the problem.
As soon as my vehicle moves, the speedo jumps to 25 mph, then behaves normally. Once my speed exceeds 25 mph the cruise control also works normally. It continues to work normally up to a speed of around 50-60 mph and then it starts to dither and fall off. The cruise control also stops working.
Once I reduce speed to say 30-40 mph, the speedo and cruise control begin working again. If I stop the car, run in and out of a shop, and re-start to go to my next destination, and the sequence repeats all over again. Sometimes the speedo will hang in at freeway speeds for a few miles.
The speedo is driven by a sensor in the differential. Check to make sure the wires at the sensor are making good contact.
There have been cases recorded where dry joints in the speedo head are the cause of the problem, especially in damp weather.
Volvo 940/960 models were introduced to the market in autumn 1990.