Hi Scotty, my 2003 suburban (base model) AC was only blowing air through the defrost and heat. I heard this is the default mode for safety.  I had to replace the actuator located underneath the radio.  I opened the original actuator and found the gear had cracked.  I also replaced the AC control module because i broke one of sliding temperature lever.  I reset/reprogramed the system and it worked but when I change the dial from vent to other modes like defrost or heat, the system gets stuck and only blows air through the defrost and heat no matter which setting I select.  I have to reprogram the system to get it working. It has done this a few times now.  Any reason why it resets to the default setting.  Thanks a bunch. 

Arndios