The odometer is mechanical and subject to odometer gear failure. A tiny little plastic gear in your odometer has lost a tooth or two which makes your odometer inoperative. Mine failed last year in my 1996 Volvo 850.

You may go to the dealer who will try to sell you a whole new instrument cluster costing $690 plus labor or go to odometergears.com. The fellow who runs this business sells the gear for around $25. You must remove the instrument cluster from the dash, disassemble the cluster to access the odometer and disassemble it to access the gear. There are two types of gears, one has more gear teeth than the other. You must note how many teeth your gear has and order the correct new one. Do a search using the words"Volvo 850 odometer gear failure" and a site will pop up with instructions on how to disassemble the instrument cluster. Check Bay 13 for instrument cluster removal instructions. Micro torx screwdrivers are required to disassemble the cluster.

I is amazing that a gear so small can cause so much trouble. Small wonder that all new cars have electronic odometers and trip meters. (no gears to break).

Dan