To fix your car's faulty heating system, you first need to have a basic understanding of the situation. Is the heater blowing cold air into the car, or is the car heater not blowing any air at all?

These instructions will help you diagnose and repair a car heater that is blowing cold air. If the heater is not blowing air, go to the next section.

Check the coolant level. Turn the vehicle off and allow the engine to cool completely. The coolant is located in a clear plastic container in the engine compartment. It should have level indicators that show how full or empty it is. If the coolant level is low, the vehicle is probably not circulating enough antifreeze through the heater core and will need to be refilled.

Check the heater core temperature. Lift the hood and check the temperature where the heater core hoses enter the heater core housing. The safest way to do this is with a non-contact infrared thermometer. If one hose is the same temperature as the coolant and the other is cold, there may be a blockage in the heater core. If the vehicle has a valve on one of the hoses, check its operation. A stuck valve will prevent coolant from flowing through the heater core.