I have a 2005 A6 3.2 and have been having some annoying trouble with the automatic climate control. Periodically, with the temp set anywhere from 64 to 69 degrees, all of a sudden the vents in the back seat area and the outside vents up front start blowing very hot air very hard, while the center two vents up front are blowing very cold air. There's no pattern as far as it happening on very hot days or mild days, and for a while running the dual zone on SYNC helped, but then it started doing it again, and if I turned the temp down to LO for a couple minutes it would all get back to normal but that's also not helping anymore. I was just wondering if this sounds like a sensor problem or if it's a known issue? The vents blowing cold are very cold and the hot ones are very hot, so it doesn't seem to be a total system malfunction. Any suggestions?

 

Mine does something very similar. If it's not in the "Lo" position, it blows hot air out of the outside vents. I haven't looked into it yet but looking forward to see if anyone has an idea.

 

It is a common problem with the C6. Drop me a PM with your e-mail address and reference that you have the problem with different AC temperatures between inner and outer vents and I will e-mail you the TSB.