2001 Durango SLT blowing hot on DEFROST only.
 

Figured i might find some help here before i start tearing the dash apart. Seem to be having a few issues with heat front and back. I get hot air in defrost mode, vent is luke warm at best and floor is cold... air flow switches properly between all settings, just not the heat. Does anybody have a diagram of the whole front heater assembly with an arrow of what actuator might be causing this or could it be a vacuum issue? My rear heat is a separate issue which has me slightly baffled at the moment. Both lines on heater core are hot but as soon as i turn on the heater, air goes cold as do the heater core lines. Brand new heater core as old one was plugged up. Blend door working properly so what does that leave me with? Water not circulating properly?

Try bleeding the system. weird things happen when there is air in the cooling system

whats the easiest way to bleed it? Just had coolant system flushed drained and refilled so maybe they didnt check...

Take it back to "them" and explain this new situation since they just worked on it.

I would have to double check but, I think there is an Allen screw on the upper radiator hose near the radiator cap (not the plastic overflow). this is used for bleeding the system. Your Haynes or Chilton's should give good instructions on this procedure. it is pretty easy and only takes a moment or two.