I just received as a gift, a 1987 Volvo 240 Sedan, and I've been driving it for one week. The previous owner took great care of it, but today as I needed to turn on the headlights for the first time, something weird happened - The temperature gauge was dangerously rising. When I turned the lights off, it would start to decrease...and when I don't have the lights on, the gauge is right in the middle, where it's always been.

I've never thought that turning on lights would or could affect the temperature gauge....please advise because I am stymied..thanks,

 

might be a dirty ground.

 

Does it rise with the just the parking lights on or do the headlights have to be on? My thoughts are some sort of short circuit on the instrument cluster circuit board. If the temp rises with just the parking lights on, then I am thinking that there is some sort of short between the instrument lighting and the temp guage. Also, you could try to dim the cluster lighting to verify this (dim the lights, temp go down?).

If you confirm the above, I would pull the instrument cluster out and inspect the circuit board on the back looking for burnt spots, bad solder joints, etc. Also, clean all the contacts with electronic contact cleaner as this Pierce suggested.

 

I haven't tested it with parking lights....I will be away from the car for a few days, but when I am back I will test out some of your suggestions...thanks so much for the input.