My heat gauge is not working. Sometimes it reads hot, sometimes cold, and sometimes in the middle. If I unhook the wire on the sencer, nothing changes. I have had the dash out and I replaced the voltage divider and even the gauge and nothing changes. Sometimes when it is reading hot, if I bang on top of the dash, it will seem to read normal for a while. I checked all the wires and can find no problem. Does the circuit board have a habbit of breaking? I can'tsee any problem there either. What do I check next please?

Thanks loads for the info you shared, hell of a lot more than the Volvo agency would do. Your advice was good and the gauge works perfect now. These guys wanted to fix it but for hundreds of dollars and I almost went for it. All I can say is THANKS, THANKS, THANKS again! Wayne

Very common problem. Temp compensation board. You can try to fix the board, or remove it entirely and solder a wire in place to cary the current. Check out the link below for instructions and rationale. Easy fix, about half an hour. Did mine a couple weeks ago and now it works great.

http://www.brickboard.com/RWD/index.htm?id=580670

Good luck. 1987 245DL, 228k

Your problem is most likely with the temperature compensating board. It is a small, approx. 1x3", circuit board inside of the instrument cluster. If you changed the gauge, you probably looked right at it. Anyway, remove it, clean its contacts and resolder all of the connections on the board. This usually fixes the problem. Do a search of this board for more info. THis topis has been discussed in detail countless times. Good luck.
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'86 240(original owner), 225K, Boulder, CO.

What year?

it is a 1988 240 Thanks Wayne