2021 Suburban Premier A/C temperature problem

[Scribe325]

2021 Suburban Premier with about 75K miles. 

Short version: Driver side A/C won’t get cold. 
 

The air conditioner is working properly on the passenger side only. On the driver side, when the passenger side is cold, the driver side isn’t. It’s not exactly hot but more like ambient temperature. When I set either side to a hot temp, both sides heat up properly. Same behavior with “sync” selected or when setting each side independently. Rear temperatures also work properly. 
 

I have checked the refrigerant, replaced the blend door actuator, and tried multiple different calibration methods. No change. The dealers in this area are a non-starter. I have been to a couple of them in the past and they routinely misdiagnose problems with the most expensive, but incorrect, repair. I don’t trust the dealers to do anything but collect my money. 
 

I’m running out of ideas. Google has failed me. Any thoughts from you A/C experts?  Thanks in advance. 
 

Alex

[davester]

I would pull off the blend door actuator and feel how it moves when adjusted manually.  Then see the range the actuator moves the door through when changed from full hot to full code, to see that it matches how far the door moves when moved manually.

[davester]

a more advanced code reader may find codes in the hvac system that can point you in some direction.

[newdude]

Its either low refrigerant from a leak or the doors in the heater box for the passenger side aren't working right (broken links).  We just had a 2025 HD in that had a leak in the line at the compressor and refrigerant was low.  The low refrigerant led to the AC blowing cold on the passenger side and hot on the driver's side.  

Edited July 7, 2025 by newdude