GMC 2003 truck heater/ac not consistent.

Do you know how to do automotive electrical testing ? Videos on youtube showing how to do it . Does your Yukon have manual or automatic Heater/AC system ? Could be the blower motor is bad , blower motor control module (if automatic ) Do you hear the blower motor running ? 2005 Chevrolet Tahoe Blower Not Working Chevy GMC same thing

Yep, when you put the new battery in, it blew your actuators, PIA job, but can be done. You can TRY disconnecting battery again, but I'm betting your actuators just blew. Very common problem with our platform, poor design.

I think your problem is the head unit that selects where the air comes out ie. Face, floor, defrost, or hi-level face and floor. If that's not working then it will not let you switch location that you want the air to come out.

A vacuum hose that controls the little door that switches where the air blows from is off, its gonna be a real chore the find which one and take the dash out to get to it, but you might get lucky and be able to look underneath the dash from the passenger side and actually see it, good luck

no,, the system works from a vacuum and has to be worked on in a service garage. sorry about the bad news...

had this trouble in a dakota it was a blend door in the heater unit. had to remove entire dash to repair

Sounds like a vacuum leak. Check the vac supply on the intake manifold. Passenger side front of intake.

Check the vacuum hose going to the heater control valve,it may have popped off. If that is on. check the vacuum hose going to your recirculation door under the right side of your dash. I hope this helps.

common problem, check under dash by the gas pedal if control arms are muving went selecting from ac to heat cuz this it is the control for the vents to go from ac to heat and to defrost.

I HAD THE SAME PROB WITH MINE I REPLACED THE HEATER CONTROL PANEL & IT FIXED IT