2008 GMC Yukon fan blowing while the vehicle is turned off

[Landon Caldwell]

My 2008 GMC Yukon will occasionally blow cool air out while the car is parked and the keys are not in it. After it does that it seems like when I turned the air on it has a mildew smell. There is not cabin air filter in my GMC Yukon because I have taken it to the dealership to get a new air filter and there isn't one. I have it at the garage now to get new shocks on it and wanted to get this problem fixed while I have it there.

[Landon Caldwell]

Yes when my car is off the fan blows. It only does it when it is hot outside. Normally it will blow cool air

[Doug_Scott]

The way your post reads, you are saying that the truck will sometimes turn the HVAC fan on while parked and no keys in ignition, so ignition is OFF. Please confirm that is what you intended to post.

 

Mildew smell could be as simple as the cowl drains are blocked. Look on the firewall around the HVAC unit for a short rubber tube that appears to have its open end sealed shut. Once you find the tube, squeeze the bottom of the tube and that will open it allowing anything inside it to drain out. Generally the water can leak out this tube, but, if it gets plugged or partially plugged, the water will just sit in the cowl and become home to mosquito nests.