Anyone know what might cause the heat to blow cool air and the a/c to blow hot air? Happens intermittently. also the heat and defrost to not work well and the a/c is not great when they seem to be functioning properly.

thanks

2003 gmc yukon xl

Gremlins. Or, a sticking blend door in the HVAC system.

Ha. could be gremlins.....whats a sticking blend door?

The blend door controls the mix between hot and cold. You probably need a new blend door actuator which is located above the hush panel in the driver'* foot well. Do a google on 2003 Yukon blend door actuator location and you will find youtube videos and various posts with pictures.

thanks, is there more than one in the truck? I have rear heat and a/c also. the rear works fine. the front dash vents and floor vents blow luke warm to cool air when heat is on. do you know how much cost to fix is?

thanks

I believe there is more than one, but someone with more knowledge about your specific vehicle may be able to confirm. As far as expense, it depends on whether you do the repair yourself or not. You can get the part from $30 (Dorman) to $100 (AC Delco). There are several youtube videos on how to change them if you want to get it a shot. Not a very difficult repair.


Typically what happens is the plastic gear inside the blend door actuator cracks or breaks.