I have a 99 Chevy Blazer that blows hot air constantly in the cabin. Is there a vacuum line that could be loose somewhere that's causing this? Someone said something about an actuator door as well. I'm not car educated enough to know why it's blowing so much hot air at all times. Summer makes it miserable too...

 

Are you saying that hot air comes out of the vents at all times?

If so, the sounds like the blend door (blends hot air from heater core and cold air from AC evap coils) is stuck in the hot position. This could be due to a failure of the actuator motor that moves the blend door, or the blend door has broken.

The glove box or dash storage compartment...whichever term applies can be opened and the door dropped down by lifting the latch. Check-out YouTube for videos about this and probably the blend door actuator as well. I will tell you that replacing the actuator is difficult due to the very limited access to the mounting screws....but can be done.

Let us know what you find out.

 

Does it do it while the HVAC controls are off? I have the prob as well with my 01 with auto climate, and even when I turn the controls off, the blower motor is off, hot air is still trickling out through the vents. (without as much force obviously)

The HVAC on this vehicle is enough to drive someone to drink.