not blowing air through dash vents

[Petey!]

check to make sure you can turn the fan on and activate your a/c system first. if not and you only have floor vents go after your fan switch first.

Alright will do. When I press AC the light doesnt activate, same for interior ciculation, but defrost comes on.

I havent had AC since I got the truck but I never got it looked at to see why its not working either.

 

[BanOne]

AC through defrost vents only

Sorry to revive an old thread but this just started happening to my wife's 02 Yukon XL. Had a battery problem(loose positive terminal) and she let a couple tennis friends mess with it and I think when they jumped it and put a charger on it some thing got fried because the ac only blows through the defrost vents and the gas gauge was pointing straight down. So is replacing the ac control head unit in the dash the solution? I messed with the temp actuator door already and that is working so it is either the head unit or the mode actuator door that got fried. Does anyone know where the mode actuator is? There is a harness just to the right of the temp actuator door just in front of the blower that looks like it could be it but i am not sure.

Thanks in advance

Doug