Anyone ever experience a possessed temp gauge? When I run the AC every once in awhile the temp gauge shoots up almost into the red. But the first time it did it, by the time I got pulled over to check under the hood it fell back to normal 210 /215 range..... not slowly.... like the way a fuel gauge goes up when you turn the key on. It's done it twice now and the engine didn't seem
overly warm or run any different. Any clues where to start?

 

check the wires for your temp sensor? it could be grounding out some how...maybe im missing something obvious but that seems really weird.

 

checked the wires, everything looks good, I'm still at a loss, I can't think of
anything that would be shared between the AC and temp gauge. But wiring
is something I'm not well versed in.

 

you and I both. I guess if you verified the engine is at operating temp when the gauge decides to have a fit, no harm done? Not a good answer i know lol.

 

Try checking the resistance of the braided ground strap that goes from the engine block to the firewall, if it's high, replace it.

 

Exact same thing happened to my brothers grand Cherokee. We thought it was a fluke in the gauge, but it was actually over heating! I can't remember exactly what the issue was, but i want to say the AC pulley was seized/locked up so when you turned on the AC the belt froze in place and as a result, did not rotate the water pump causing it to over heat.

With the engine running, open your hood and study the AC compressor/pulley as a buddy turns on the AC from inside the Jeep. This may give you a better idea of what's actually going on when you turn on the AC.

Just my .02, good luck!

 

Went through this with daugters Volvo. Overheated when A/C was on. To make a long story short it was the fan clutch.

 

Awesome, i'll check out the fan clutch, AC pully, and the ground strap.
Been planning on upgrading the grounds anyway. So now seems like a
good time to do it.
Thanks for the ideas!