Hello, I am a new memeber and have recently purchased a 2007 a8l (my wife has a 2005 a6). I have an issue with the ac system where the outside vents blow hot and the center stack blows cold. I have taken it to the dealer and the only error code that comes up is for a rear footwell heater. The next step would be to replce the ac control head but this is a very expensive part ($1200 front, $450 rear). I have seen a thread for the A6 where there was a tsb for this issue and they replaced a defective pump valve. Any tips for this issue?

Otherwise I am very happy with the car.

 

I've seen this happen before on an 04 A8 we had for sale at our dealership. For us it ended up being stuck flap. Not fun fixing it, have to take a lot apart. The flap is inside the dashboard, towards the heater core. There is a way to diagnose this with VAG-COM if you have it.