Most Gm cars are set so when you turn the air on, the cooling fans come on. Do you have an overheating problem?
The fans are set to come on somewhere around 235-240 degrees without the air on, and I think this is too hot. When the car was new, the temp would go up, the fans kick on, and the temp would drop to about 200. After the car ages a few years, the radiator gets some gunk in it, and the thing just doesn't cool like it should. Best thing to do is just leave the air on. The other alternative is to get a HyperTech chip that runs the fans at a cooler temp.