Q: My car is overheating when the air conditioning is on - 2007 Hummer H3

Hello. Running the A/C will put extra strain on the engine and cause it to heat up quicker. If your vehicle is overheating, you should keep it below 280 degrees at all cost. This is the temperature when extreme irreversible damage is done to the engine. You can even run the heater, which uses heat from the engine to heat the air, to cool down the engine.

You will want to start by checking your coolant level. If the level is full, inspect the thermostat and the water pump. Both of these can fail resulting in poor or no coolant circulation. The circulation is critical for the heat transfer that must take place. If the vehicle is low on coolant, you need to determine where the fluid is going and where the leak is coming from. Any leaks will need to be repaired and the cooling system should be tested for proper function.

I recommend having a certified mechanic, such as one from YourMechanic, come to your location to determine why your car is overheating and what should be done to get it back in full working order.