Climate control suddenly blows cold air with heat on

[HUMTECH]

You can take it to the dealer and they can try an HVAC door relearn procedure with A tech 2. Also you may have a blend door actuator going bad and intermittantly defaulting to the cold position.

[lasvegash2]

i am also having the same issue, i set it to 80 but it blows out cold air every so often. when i turn the iginition off and then start it back up, it works just fine. one other problem, when i have it set to auto and i start the truck up, i get a buzzing sound from behind the dash, almost like actuators sticking or something.