We had the exact same thing happen to our 2011. There are 3 actuators. The one that fixed ours was the one way up in there. The MIX actuator, I believe.2012 Enclave, 116K miles. The passenger a/c blows hot air; all other a/c vents blowing cool air. I pulled up a video that said it might be a bad actuator; my friend replaced the actuator, still the same problem. Any advice would be appreciated.