Repair a Car Heater

A car’s heater simply circulates some of the hot coolant from the engine through a device that looks like a small radiator and then blows the resulting warm air to heat the interior of the car. By this description, you can identify the main parts of car’s heater: the heater core (radiator), blower motor (fan), and hoses.


  1. Inspect the heater system for blockages and broken parts. Make sure the heater hoses are in good condition. If your car has a summer valve on the engine block, make sure the valve is open.
  2. If necessary, check the blower circuit and motor. If the blower motor isn’t operating, check the fuse and all the switches and wire connections. Some blower motors also have resistors that can burn out and need replacement; you can check them with an ohmmeter.
  3. If the blower motor needs to be replaced, follow the instructions in the service manual for doing so. In some cases, the dashboard must be partially disassembled. In all cases, you must first drain the cooling system.
  4. If the heater core needs to be replaced, again, follow the instructions in your car’s manual. There are just too many ways of doing so to cover them all here. The heater core is typically found in a housing unit under the dashboard or in the engine compartment against the firewall. Disconnect, disassemble, replace and assemble.
  5. To test your car’s heater, repeat the earlier procedure for purchasing ice cream. If it melts before you get back home, the heater works fine.



  • An ohmmeter is a handy device that measures resistance in an electrical circuit. If resistance is infinite (1), the circuit is open and won’t pass electricity. Use an ohmmeter that also measures voltage, called a volt-oh-meter (VOM) because it can also tell you how much electrical voltage is in a circuit.

Related Articles