I've had some issues with the air con / climate control system in my a3. The main symptom is that when its set to low or a cooler than ambient temperature there is no cold air and theres no click sound from the clutch when it's activated.
I've had an air con specialist look at it which first of all meant regassing the whole system but the compressor wasn't running.
We disconnected the power to the compressor and plugged it into a volt meter - interestingly when the a/c was off or on (turning off either by pressing Off / econ / setting a high temp) there was always 9v registering on the volt meter. I expected to only see the volts register when the a/c is on.
Firstly is this normal behaviour? If it was that there was only a voltage showing when the a/c was turned on then I would happily point the finger at the compressor but if this isn't the normal what's the next logacal step for me to go through so I can enjoy nice cool air once again.