Chrysler Repair: Heat and Air, dodge ram 1500, air fan

Question
2001 dodge ram 1500 5.2L.
Mr Finston, my truck heat and air fan works fine but when adjusting the thermostat there is no change from hot to cold. I put it on Max AC and there is no change. Turn the heat on high and no change.Both controls were affected at the same time. What are the possibilities here?
Thanks
Tom

Answer
Hi Tom,
There is an internal door in the air distribution box under the dash called the "blend air door" or the "temperature door" which is either controlled by a cable attached to the temp lever (conventional) or by a small motor(automatic temp. digital display type of unit). So if it is the conventional unit, remove the heater control panel and see if the cable has come loose from the lever that operates the door or the lever has detached from the door. Otherwise, the door motor may have gone bad if you have the automatic control unit (the motor is often placed on the under side of the unit).
This is all based on the car design; I don't have any experience with the truck system but it should work the same way in principal. The temp door controls what fraction of the total air goes thru the heater core (after having first been passed thru the ac coils) or if it by-passes the heater core entirely. That is how the outlet temp is adjusted.

Roland