Climate control suddenly blows cold air with heat on

[SnakeH2]

Originally Posted by BlueHUMMERH2

When I had this problem, I was blowing cold on one side and hot on the other....

That's happened to me a couple of times. I shut the whole system down and that seemed to correct it.

[ree]

First time for me too was left only. The time today was both.

I just took a look in the service manuals. Perhaps I'm not looking in the right place, but all the HVAC door replacement procedures (Recirculation, Mode Upper, Mode Lower, Air Temp Door Left and Air Temp Door Right) start with "Remove the HVAC module assembly" which starts with "Drain the engine coolant" and a bunch of other stuff that doesn't look too simple.

I haven't yet searched the manual enough to see if there's a simpler procedure to get at the doors enough to inspect them. If I figure it out, I'll let you all know.

I really seems like a software/firmware bug though or maybe some sensors that indicate the orientation of the doors (wild speculation).

[Goalkeeper]

I also had this issue happen for the first time recently. Instead of hot air for the center right / right, I was getting Cold air!

It hasn't happened since and only that one time....so far.

[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.