My 04 Yukon XL has the automatic climate control. I can feel cold air at the vents, but the fan does not change speed, whether it is manually changed or on auto. Sitting still you can just feel the air at the vent , but at highway speed it is being forced out. The rear a/c is working fine, I think it is a separate system though. My battery died the night before the problem started, could this have caused a problem? I am the original owner and I have never had a problem with it.