2003 Pontiac Vibe Base 4 Cyl 1.80L
Why can I not adjust the temperature in the cab? It's either full AC or full heat
The AC works great when on Max., however it doesn't blow cool air when on regular AC. The heat works good also when the selector knob is on heat. The problem is when I rotate the temperature thermostat knob, it doesn't adjust the temperature flowing out the vents. I can not achieve a comfortable temperature in the cab.
Check these two (2) possible items - the heater blend door actuator and the a/c - heater control switch.