Help. AC was working normally, selected defrost, now will not come out of defrost mode. Blowing full heat from all defrost vents. Both front and rear mode selection dials do not change anything. Only thing I can control is fan speed and turn off. Is there a TSB for this or DIY reset procedure to fix?

 

Update: After sitting in the parking lot all day, I rotated the mode selector switch slowly through all modes and it moved out of defrost mode. Also had to cycle the temperature dials from cold to hot to cold again. Repeated same procedure for rear A/C controls. I've read about a reset procedure for earlier year vehicles involving removing and reinstalling the A/C fuse. Still would like to know if there is a real fix out there if this happens again and what is the root cause for this.

 

A year later and this problem is back again, selected defrost and now will not come out of that mode. Rear HVAC control stuck in defrost as well. Can't seem to find any posts for this problem on my generation suburban. Any help is appreciated.