Q: My car is overheating. The engine fan does not work unless the air conditioner is running.

Many vehicles have two separate fans. 1 fan is used for the engines radiator. The other thing is used only when the air conditioning is running. The fact that a fan kicks on when the air conditioning is running as a normal operation of your vehicle. If the engine is overheating and your cooling fan is not turning on it is likely due to the fact that the cooling fan is not working. Symptoms of a cooling fan failure would be that the engine runs at a normal temperature during highway speed but during slow driving or idling the engine temperature will rise. I would recommend having your engine cooling fan tested to determine if it is working properly. If the fan is faulty I would recommend having it replaced in order to avoid permanent damage to the engine that could be caused by overheating.