I have 92’ GMC Sonoma. My water temperature gauge has given up the ghost. It is now pinned as high as it can go.
When I got my heater core replaced I had them check it out, apparantly it is the gauge that has busted not the thermistat. They wanted $75CAN for a new gauge and $85CAN to put one in. No thanks, I think I’ll put a after-market gauge in myself.
However, I do have a question, currently because my old gauge is maxed-out my “Check Gauges” lamp is lit up, if I by-pass my stock gauge will my “Check Gauges” lit go out?
If the "check gauges’ light is lit up, I’d be inclined to suspect the gauge sender (screwed into the engine, probably near the thermostat housing, near the engine end of the upper radiator hose) rather than the gauge itself. Replacing the sender is not a big deal.
If you added an aftermarket gauge, you’d have to replace the sender anyway, since I doubt it would be compatible with the original GM sender. My advice would be to find the sender under the hood and disconnect the wire; see if the gauge moves. Touch the wire briefly to a ground; see if the gauge moves. Movement of the gauge implies that it’s okay, so in that case you replace the sender and everything is copacetic.
The “Check Gauges” module is connected to the sending unit circuits for the gauges inside the instrument cluster. If the problem is indeed with the gauge itself, you’d have to do some electrical surgery in the cluster to get the light out.
If the shop misdiagnosed it, the problem is in the sending unit on the engine or the wiring between it and the gauge. Replacing the sending unit is fairly easy. Tracing a wiring problem could range from easy to devilishly difficult.