HVAC through Defrost Only, Multiple Resets, What's Next?

[lawfarm]

2007 GMC Yukon SLT. Auto climate control (dual zone) with auxiliary rear climate.

Roughly 125k miles.

A few weeks ago, I had the 'heat only through defrost' symptom, and only heat, no matter what I set temp or zone to. I did the 'pull fuse' reset trick and it worked./

Yesterday, without warning, had the same issue. Pulled the fuse for reset, and it worked again. When it's working, all controls work; you can adjust the temperature hot or cold, and can also adjust what zone you're pushing air to (floor, mid, defrost).

What concerns me is that this has happened 2x in about as many weeks. Yesterday, resetting took place in a freezing parking lot, because otherwise, I had no floor heat. What's the next step? Replace the HVAC control panel under the radio? Other?

 

[swathdiver]

Use your Tech2 to identify the offending actuator and replace it. The codes will follow with a symptom number telling you exactly why the actuator failed.

B0228 is for the recirculate actuator.
B0413 is for the drivers air temperature actuator.
B0423 is for the passenger air temperature actuator.
B0433 is for the auxiliary air temperature actuator.
B3779 is for the mode actuator.
B3782 is for the auxiliary mode actuator.

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