Nissan Repair: Heater Problems 99 Maxima SE, 3.0L V6, 5speed, heater core, heater fan

Question
Von
I have a 99 Maxima SE, 3.0L V6, 5speed with a heater problem.  The Heater fan works, the AC blows cold, the Heater thermostat activates the Fan and AC with-in 0.5 deg. However I am not getting any hot air blowing into the cabin.  There has been a new radiator, thermostat, hoses and pressure test done in past year. Could this be a Heater Core problem, if so where do I located it and how difficult is it to replace?
Thank You

Answer
Robert,

The heater core could be blocked internally.  That is, the core could be plugged.  It is in the dash on the passenger side and is quite the pain to replace.  That would be my bet since you say everything else works and the new radiator would lead me to think the heater core was not far behind and that means it is probably plugged.  Another cause would be the blend door sticking where it cannot get heat out.  To check this, get the car to operating temperature and feel both hoses that go to the firewall.  If both hoses are warm then the core is fine and the blend door is not working.  If one hose is hot and the other is cold then the heater core is defective as in plugged.