ok i have a 1991 740 turbo volvo wagon with 193000 miles on it the speedometer sometime works sometimes doesn't i could be driving down the road going 50 mph and the needle drops to zero then it goes back up or sometime im driving i have been doing 30 mph and it just drop back to zero and stay there now when i turn the key to start the car the needle jumps sometimes not all the time but i have checked the speed senor in the diff its working fine nothing wrong with it i have pulled it out checked it cleaned it up and put it back in it reads i have checked the wires the run from the speed senor follow them to this black box?? i have no clue what this is tho the wires from the speed senor to this black box are in good shape also my ABS light is not on at all ABS works fine so thats not it but i dont know it is or whats causing it??? and thats this black box that those wires from the senor go to and form the other end of the black box theres is other wires the black box is in the driverside compartment where the tank fuel pump connecttion

 

OK, I guess you are saying that your speedo is not working sometimes. It is a common problem and it is most likely internal to the speedo. Some of the diodes go bad... Speedo shop or another speedo is the answer, or you can re-solder new diodes in.

 

hey thanks thats what i was aftrid of well its not my car my step dad car he couldnt find the problem so i posted it lol to ppl that know way more so thanks