I have an 08 4.3L GMC Sierra (35000 miles) that for the last 4 weeks has had an odd temperature gauge problem while driving to work. The temp gauge will quit working and I will get a - hot engine ac off - message on my driver info center. The ac will not work and the radiator fan will kick on and run continuously. The truck is not running hot. After it sits all day it will still display the warning until the temp gauge comes back up. Then the air will work and the radiator fan will kick off. The really odd thing is it does after driving 15 miles + or - a couple of miles in the morning. Then on the way home from work everything will go back to normal after driving about 3 miles. Week before last it did it every day ,but the other 3 weeks only once or twice. Never did it on the way home. Think this might be a sensor problem or the temp gauge failing? Will not stay screwed up long enough on the way home from work to plug the computer in and get it checked. Drove it over 30 miles last weekend trying to get it to mess up and it wouldn't.
thanks for any help or thoughts on this - mike

 

I'm a little confused by the radiator fan running continuously (I assume it's not electric) but otherwise I think your instrument cluster is acting up. The gauge quits working and you get the hot engine message, they are from the instrument cluster logic.