One or more heater & AC (HVAC) temperature and/or air delivery mode door actuator may fail, resulting in improper temperature or air delivery. If this occurs, fault code(s) should be stored in the HVAC control module which should assist in diagnoses.Google+
Car Problem Reports
GMC Sierra 1500 Heating and AC Temperature and Air Delivery Mode Door Actuators May Fail
GMC Sierra 1500 Problem
Average Mileage: 118,070 mi (46,000 mi - 210,000 mi)
Visitor, 2004 GMC Sierra 1500, 114,000 mi
This is a well documented problem as you can see by reading articles throughout various internet sites. For being the so called a "Professional Grade", I have had so many problems with my GMC, from the instrument cluster, steering column, bed liner, hubs, ABS, emissions, etc.... and now with the HVAC - I'd give my 2004 GMC Sierra a disappointing "F". GM needs to issue Campaign to correct this problems, since so many of their customers are experience problems due to their poor workmanship or inferior design.
A/C only cold on passenger side. Drivers side blows hot. There is no adjustment on the drivers side for temp. If you turn off the truck and then restart, it might work for a bit or not.
Visitor, 2001 GMC Sierra 1500, 75,000 mi
Can't change heating/a/c temp unless I shut down truck and reset to desired temp and restart, then it goes to correct temp
Visitor, 2000 GMC Sierra 1500, 145,000 mi
textbook problem like all others. Temp. adjuster knob when turned to cold would only blow hot all the time. Actuator is at fault.
Visitor, 2000 GMC Sierra 1500, 210,000 mi
system won't deliver to air flow to the proper place, ie defrost,floor,or ac vents.
Visitor, 1999 GMC Sierra 1500, 164,322 mi
When selecting where i want my air to go, it only comes through the vent at my feet and through the defrost. The dash vents do not blow any air. It seems like a common problem. Im gonna go ahead and replace the mode actuator!
Visitor, 2001 GMC Sierra 1500, 151,000 mi
Heat vent operation will only blow on the floor and windshield defrost. Does not change position when the nob is turned.
Visitor, 2000 GMC Sierra 1500, 199,589 mi
i have problems when i u the air or heater.i have to shut the car off for half hour before i can u the other
Visitor, 2003 GMC Sierra 1500, 63,000 mi
heat only at 90 deg.
Visitor, 2009 GMC Sierra 1500, 50,000 mi
The air is stuck on cold. If you turn the dial to hot to defrost the windshield the temp. will not change.