2006 Hyundai Elantra • 165,000 miles

My heater does not blow hot when the fan is turned on. If it is off I can feel the heat from the vent but it will not blow hot. I just had a new Radiator, hoses and a new thermostat put in and it still is not working correctly. Could it be possible that the door that normally opens when I have it set to cold is not shutting? It is very cold and I am at my wits end. Please help
December 20, 2012.

See if both heater hoses going into the heater core at the fire wall are too hot to hold when the engine is at operating temp?

Dec 20, 2012.
I believe you are referring to the blend air door, and yes that can be what is causing the problem for you. If it doesn't function properly, you won't get heat. Also, make sure that both heater core hoses are getting hot. If they are, then the core is working. If only one is hot, chances are the core is plugged, One last thought. Even though you replaced the thermostat, make sure the engine is warming up to operating temp.