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Denali Heater

I have a 2005 Denali XL. The front heater was blowing only cold air set at 90deg. and the back was blowing hot. I tried a few internet tricks (taking out hvac fuses, disconnecting battery, etc) then they would both blow only cold air. Now the front and back are blowing lukewarm air with the passenger’s side front blowing slightly cooler. I have read about it possibly being an actuator. Don’t think it’s the heater core but how do I tell for sure? Any suggestions?



First thing to check is the coolant level in the radiator while the engine is cold. Make sure it is full and there isn’t any air bubbles in the system. Usually bubbles will make noise while the engine is running if they are present. If that is ok then perhaps the problem is with the air blend doors or the HVAC controller.

Thanks for responding