the 01 FSM calls out the A/C Heater control, the blend door actuator, or the blend door itself.
The temp control is vacum actuated. the blend door is also vacum controlled with an actuator.
Check the vacum lines behind the A/C control panel. Pull the glove box, and the center bezel It just pulls straight out. you will see the colored spegatti. Or use a vacum gauge to check the vacum. Also check the vacum resevor (sp) under the front bumper passenger side. If the vacum lines are good, I'd go to the actuator that swings the blend door. You'll need a book for that one.