Today my car started to overheat as soon as I turned the ac on. It went all the way up to the last notch before the red zone, and as soon as I turned off the ac it went back down to halfway. It stays at it's normal point of halfway without the ac on, but as soon as I turn it on it starts to go up, and as son as I turn it off it starts to instanly head back down until half. I am planning on a thermostat change tomorrow. Any suggestions?

 

Hmm have you checked your coolant lately bcuz I believe that could be one cause of it, or I've even heard of the water pump causing problems like that before but I'm not for sure what exactly would cause that. Those are just the first 2 things I think of

 

Well today I flushed the radiator, put regular coolant in instead of that dex cool crap, and changed the thermostat but the problem is still there. I found that it doesnt matter whether the ac is on or not though. It just goes up a notch past halfway, sometimes a bit more than goes back down? And the fans are working fine

 

Man idk what it could be then. I know some people over at the monte of gm forum would prob know whats going on so maybe we could find something on there that may explain whats going on

 

which engine? - if it is something like the 3.1, these have 2 electric fans, and the second on should ALWAYS be on with the first one when the AC is on... in fact, ours runs cooler with the ac on than when it's not...

 

It has the 3500

 

After I did the flush and thermostat and drove around for a few hours everything is back to normal. I'm guessing it just had to work the air bubble out of the system from the changes but its top notch now!

 

Ahh gotcha. Well that's good that everything is working fine now =)

 

It means it was too hot out and your engine does not have enough cooling capacity to run the AC at full blast when the engine is idling. If you are stuck in traffic, turn the AC down or off if the car starts starts to show signs of overheating.

In June I was in Death Valley and it was 119F out. To get out of there, you have to make a 5000 foot climb in less than 20 miles. The car's temperature started to go way up and we had to turn the AC off and turn the heater on full blast for more cooling so the car would not crap out on us.

 

I think that may have had some factor in it, but it was definately the thermostat. I've heard that death valley even has road signs that advise you to turn off your air conditioner