Neither the front heat,air, or defrost is working. All the rear ac and heat work fine. The temp and fan gauge in the ac cluster shows that its working but nothing is coming out the vents. This happend all of a sudden, everything was working fine. This is in a 07 yukon denali.

 

Did you check all the fuses? Sounds dumb but you'd be surprised how often fuses cause problems.

 

Yeah, I checked the fuses. I'm gonna check the relays this evening. Just wondering if this has happened to anyone else.

 

Does the front blower motor come on? If not possible causes are a fuse, blower module or faulty motor.