2002 Tahoe stuck on defrost tried replacing EVERYTHING, help!

[Chad98]

I have a 2002 Tahoe with the automatic climate control, that’s stuck on defrost. I’ve replaced ALL the actuators with new AC delco units. No change...I replaced the control head with a used one..no change. Tried a Dorman Remanufactured unit part # 599-260 for vehicles with rear ac since mine has it...no change. So I try a new Dorman unit part number 599-215 and full functionality is restored...until I discovered now my rear ac is not working at all because this control head is for vehicles without rear ac...this tells me that the front controller and rear controller MUST be able to communicate with each other. Tried putting the correct control head back in and it again defaults to defrost and will not move. I’ve tried every recalibrate procedure known and no change. Seriously thinking about just using the incorrect control head just so I’ll have full front functions but I REALLY want both front and rear to work as designed. Anyone have any idea on WHY it defaults to defrost with the correct control head, but functions fine when the incorrect control head is installed? (I just lose rear air)

 

[Fless]

The easiest/quickest way to diagnose it is to get a Tech 2 or other bidirectional scanner on it to see what's commanded vs. actual. Has it been recalibrated with a Tech 2, or just manual procedures?

From the part number you posted the truck should have AUTO control. Does it work the same in either mode?

 

[Chad98]

The easiest/quickest way to diagnose it is to get a Tech 2 or other bidirectional scanner on it to see what's commanded vs. actual. Has it been recalibrated with a Tech 2, or just manual procedures?

From the part number you posted the truck should have AUTO control. Does it work the same in either mode?

Yes it has the Auto control. The Chevrolet dealership tried programming the correct control head with a tech 2 and it didn’t make a difference. BTW they went through several units thinking maybe they were defective, but nope. The service manager had a near identical Tahoe so they borrowed the control head just to see if it would work but nope, still defaults to defrost. I’m wondering if the problem lies in the overhead rear climate control module since they have to “communicate.”