2006 Hyundai Elantra Repair Question
Hyundai Elantra Heater Problem
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?
23,190 answers provided
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.
57,318 answers provided