Just picked up a sierra, and everything works great, just noticed the ac will continue to blow lightly when off out of all vents. It blows ice cold when on, and heater works great, but I still feel air coming out when off. The compressor sounds fine and I checked the pressure, within spec. Just curious what the issue could be?

Thank you for your time.

 

Every truck that I've driven does this.

It can be 80º outside and inside the cab is nice and cool and you turn the fan off, but air still comes out the vents cold. I've learned to just switch it to the defrost vent and or raise the temp **** up some and it doesnt bother me anymore.

 

It's probably just air blowing through the cabin since it's being forced through by air pressure on the front of the windshield. If it happens when you're sitting still, you most likely have a defective blower motor resistor.

 

Mine does the same thing I just push the recirculate button to stop the outside air from coming in

 

If it was the blower motor resistor, wouldn't their be other issues with ac?

 

No. It only controls the speed of the blower motor. When it fails it can either stick on or not work at all. If the blower motor is still spinning with the fan turned off, the resistor is bad. If the motor is not spinning and you're still getting air, it's just pneumatic forces at work on the exterior of the car.

 

This.............