I did a quick search but couldn't find anyone else explaining my current issue. So here it goes. 03 Z71 Tahoe When stopped or at slower speeds (around town) my AC won't blow unless it's on at least level 3. When driving on the highway, it'll work on all 5 levels no problem. Goes the same for if was just the vent and no AC as well as the defroster. The rear is working fine.