I am new to this. Here is the situation on my 1992 Volvo 240 Stn Wgn with 108K miles, few months back I pushed the odometer reset while the car was running that messed up the odo, I read some instructions on the web as to remove the instrument cluster and so on.. bottom line I messed up even more. Finally I found a instrument cluster (with much difficulty as it had to be a K39200) with much difficulty at a wrecking yard. Installed it all was well for a while and one day saw the temp guage rise. Had me worried, my mechanic has replaced thermostat, coolant, sender unit, temp comp board and the temp guage (swapped with my original one). All was well and I thought my problems were over for over three weeks, day before while driving the temp guage went up again, and as usual when I turned the heater on the temp guage went back to normal (9 oclock) position. This happened again yesterday as well. Please help me what else should I be looking for ? Thanks..

Were you idling when the gauge went up? If so, your fan clutch could be the culprit.

Your problem is the !5!#@*!&! temperature compensator circuit board (99% likely cause). It lives inside the instrument cluster. Do a search in this forum on "compensator" or such, and you'll find much wisdom. I think the best solution is probably to bypass it with a small jumper wire as described in some posts, but you'll have to make your own call. Supposedly the job of the circuit board is to prevent small changes in temp reading from showing up on the gauge. When the board goes bad, the gauge does weird stuff (high, low, alterntion, you name it), and can apparently eventually read dead bottom.

In my '86, there's some kind of short between the cluster illumination voltage and the temp gauge circuit. Turning on the headlights causes the temp gauge to rise about 1/3 inch. Killing the cluster illumination via the dimmer control sets it right again, but you can't see the cluster at night that way. I haven't heard of anyone else with that particular problem, but it could be out there.

I bypassed the compensator board on my '89 240 this past weekend. Worked great. Before the bypass, my temp gauge went high shortly after starting driving, and went down only if I warmed up the instr. cluster by running the heat.

Now it rises slowly to about 1.5 mm. above the midpoint dot, and stays there.

I used a short piece of lamp cord as a jumper wire. I simply cut it, no trimming back of the insulation. I then widened the cut end of the wire by poking into it (I recommend using a small nail). I then slipped this widened wire end onto the male pin connectors. So far, so good. I believe it may never slip off - at least I hope so. It's a tight squeeze in there, not a good place for a person with my poor soldering skills to be using a soldering iron.