I've seen other threads with this same issue, but not on the GXP. Mine was garaged all winter. Noticed I have no air coming out of the dash vents when I finally took it out today. It only comes out through the floor vents, no matter what setting it is on. The auto climate and fan speeds all work however, and I turned the AC on and that is also working, just out the floor vents. No defrost either. I did have the battery disconnected while it was in my garage, so I did disconnect that again for about an hour, still same problem. Any ideas?

The mostly like cause is the same regardless of trim level. The mode actuator.

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*Gone, but not forgotten* - Black 2000 SSEi, HIR Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, 180 degree thermostat, HS 1.9 rockers, LSx yellow springs, Intense FWI, PCM, shift kit, push rods, and 3.4 Pulley. ZZP Power Log.

Thanks Archon,
After some more searching I did find a GXP thread; looks like you chimed in there too...Do you still have that diagram of the location of the actuator? I would then check to see if its moving or not. This problem is exactly like that original author of that thread, but I have not pulled any fuses. Thanks for the help.

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2016 GMC Sierra SLT
2005 Pontiac Bonneville GXP
1979 Pontiac Firebird Trans Am

I'll search for where I saved it and post it when I find it.

Edit = Found another one.

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*Gone, but not forgotten* - Black 2000 SSEi, HIR Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, 180 degree thermostat, HS 1.9 rockers, LSx yellow springs, Intense FWI, PCM, shift kit, push rods, and 3.4 Pulley. ZZP Power Log.

Archon you nailed it. Sure was the actuator. Getting replaced tomorrow. If you are ever in Minnesota I owe you a drink haha!

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2016 GMC Sierra SLT
2005 Pontiac Bonneville GXP
1979 Pontiac Firebird Trans Am

Great! Glad that you found the problem. I'd bet there are one or two MN members who would be my surrogate for that drink.

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*Gone, but not forgotten* - Black 2000 SSEi, HIR Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, 180 degree thermostat, HS 1.9 rockers, LSx yellow springs, Intense FWI, PCM, shift kit, push rods, and 3.4 Pulley. ZZP Power Log.

Piggyback on this old thread, but I am having a similar problem. Cold air out of drivers side, hot out of passenger side. I'ts playing hell on these cold days :( I had this worked on once before and i believe the tech called it an actuator module...? It wasn't corrected and he blames it on programming/software issues. I just think he was in way over his head on this. Does replacing the controlling unit always fix this kind of problem or does some sort of "programming" need done? Please someone chime in as it has to be fixed and it's heading to the dealership soon. I'd like to have SOME insight into what is going on.

It is more often than not the actuator, the climate control head unit doesn't seem to go wrong. Regardless, you can swap the units between trims so long as you find one that is auto as well.

I would bet you are having an actuator issue.

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-Car Guy Carl
"Penelope" - 2003 SLE - 247k Miles
"Sydney" - 2000 Honda S2000 - 98k miles