The temperture guage stopped working on my 01 Monte. I used the heat for the first time since summer and now my a/c won't blow cold. The car doesn't seem to be over heating or anything but when I turned the car off the fan continued to blow for about 5 minutes.

Any ideas what this could be??

 

Believe it or not, it is your thermostat. I know there is a thread about this on here. I had the same thing on my 2001 SS. What happens is your thermostat sticks open and allows for constant flow of coolant and not allowing your motor to heat up to proper operating temperature.( I'm guessing you started noticing this when the weather got a little cooler) The computer looks for a normal reading after a certain period of time and if it doesn't like what it reads then it doesn't trust the temp sensor and puts your system into protection mode. You have probably noticed your radiator fans running after you shut the motor off. T-stats are cheap so this is where I would start. Good luck and I hope this helps.