Diagnosing heater core issues

Depending upon design and size, a heater core will typically produce air vent temperatures greater than 115 degrees.  If you require more, we can add fin density but core depth is likely restricted by your plenam (housing). 

  • If the engine is cold, the heater core will struggle to heat. The heat from a heater core comes from the engine so it has to be at operating temperature to generate heat in the cabin.
  • If the coolant level is low this will reduce the heater core's temperature.
  • If the inlet hose is close to the engine temperature e.g. 190-210 degrees, the thermostat is functioning. If the engine is cold and it does not warm up, then check your thermostat is not stuck open or lower than the intended specification.
  • If the heater core outlet hose is ~10-25 degrees less than the inlet, the heater core is dissipating heat.
  • If the heater core outlet temperature is significantly cooler than the inlet, then the heater core may be clogged/restricted and require and flushing the hoses and heater core. 
  • If the heated air is hot but airflow is not strong your blower may have failed.
  • If there is not much heat, the engine is running at the expected temperatures and coolant levels are appropriate, you may have stuck blend door, malfunctioning actuator or a clogged cabin filter.  Not all components exist in all vehicles.