'09 Traverse; have been having this problem intermittently. If I have the temp toward hot, it doesn't want to go back to cold, and vise versa. I have been getting it to change just by messing around with controls. Put blower on full blast, back and forth to hot/cold, etc. But this really should be fixed. From what I gather, it's a blend door actuator.
Now I'm having another issue: I can get heat out of the bottom vents, but not out the defrost vents. I believe this function is controlled by a different actuator.
Anyone else have this type of experience with one of these vehicles. Any tips on where to find these actuators? Going to try to look at it tonight.