Air Conditioning problem
2004 Audi A6 V8 Four Wheel Drive Automatic 54000 miles
After about 1 hour of use, the air con goes all wrong. Hot air starts to blow out of one or two vents instead of cool air. Tha garage ran a diagnostic but found nothing wrong and all they did was top up the a/c fluid. I suspect that the sensors are going wrong when they get too hot. Any advice?