I'm trying to get to the bottom of an air conditioning problem I've had since buying my car a few years ago. I probably attempt to fix it every year when it gets hot. The car is actually an Audi A3 8L but it should be the same platform and the Audi forums are pretty useless so I'm hoping to find some experts in here instead that can help me before I melt.
Engine is a 1.8T.
I've just had the a/c regassed and it holds pressure. When I switch the a/c on, everything seems to work. The compressor kicks in and the revs change. The fan speed increases and the a/c rad fan also works frequently.
If I've just started the car from cold and switched the a/c on, I get cool air for about 5 minutes. Then it slowly fades to hot air. The compressor still seems to be engaged. The air does not return to cool for a number of hours - almost as if it depends on the engine being cold or the a/c not being used for a while.
I have Vag-Com but there are no faults in the HVAC. I had suspected there may be an issue with a temperature sensor perhaps but everything else seems to work ok. The dash seems to report the outside temperature correctly.
What could it be?
Thanks in advance,