I have recently bought an '89 9000 carlsson, but am experiencing problems with the speedo. For starters, the speedo does not show and information for about 15 minutes of driving, then when it does come on, the speed is inaccurate, and the needle very irratic. This last problem tends to make me seasick when trying to use cruise control. Besides the effect on the cruise control and the EDU computer, what else could be affected, ie ABS, fueling. Is it just a problem with the sender unit on the back of the clocks , the pickup itself or ©another?
I hope someone could be of assistance. Thankyou Harri.

The sender on the back of the gearbox is probably faulty. They have a nylon gear which meshes in to a component in the diff. These are known to occasionally shed a few teeth, leading to erratic speedo behaviour.

Oh yes, only the speedo, cruise control and fuel computer will be affected. It will not interfere with the ABS or fuel injection.