Blend door motor - the diverter is working (changing output from floor to dash) but its not blending the hot air from the heater core.
Pull your glovebox and CAREFULLY see if the heater core is hot... if not you have a plugged heater core. If it is - cycle the heat control - the blend door should be moving as you go from hot to cold...
Wish I could tell you how to fix it from there - but when mine went it was under warranty so I did not do any further troubleshooting.
J Wm Bishop EA, ASADE
Alcohol - because great stories never run on gasoline...