Every time I drive down one certain road and prepare to turn left (part of my morning commute) my thermostat gauge shoots to 260 degrees. But when I pull my car over to check the engine it’s cool as an engine can be after driving–not hot at all! I was driving today and noticed it jumped when I hit the brake. But I drove it for an hour the day before, hit the brakes plenty of times and it never did it. But this morning when I took it on my 7 minute commute it did it once again in the same place. And no, no hill involves, nor rain and weather.
You have a intermittent short or open electrical circuit. It is a wiring problem. Almost certain.
Yup, it’s a wiring problem.
Your temp sensor is set up such that as temperature rises, resistance drops. The dropping resistance allows more of the full voltage to get to the gage, raising the needle. You have a short somewhere that’s effectively intermittantly bypassing the temp sensor, allowing the meter to experiance full voltage and to peg.
I’d start looking at the sensor end of the wiring. That’s the part of the wiring most exposed to the possibility of insulation damage that could result in shorting.