I had the AC on when it was hot and humid one day. Saw the temp bar go up to 4 bars. I shut the AC off & it went back down to 3 bars. Well today its hot again & I used the AC. This time I kept driving to see if it goes to 5 bars but no. It'll be @ 3 bars then up to 4 bars & after 30 seconds or so it drops back to 3 bars. This is with the AC on. Could it be my thermostat or something else?

 

The ac radiator sits infront of your engine radiator. When ac is on, it gets hot so the air going to the engine radiator is "preheated". This makes your car run hotter with the ac on. What your seeing with the temp bars is the engine temp being just at the spot between 3 and 4 bars. A wash slightly cooler air in through the front could make it drop back to three or driving behind another car could drive it up to four. I wouldnt worry.

 

^ thanks.. I've been driving it with the AC on to see if anything goes on & it seems ok. *phew* Thanks again.

 

drain the coolant fill it up make sure its at the proper levels... mine did the same thing was just low on coolant.