I have an Audi A3 1.8T (1999) with climate control and have been having issues with my air con that seem to be getting progressively worse over the last few years. Firstly I've had it regassed twice now but it doesn't make any difference. If the A/C is set to Auto and the temp set to LO (i.e. below 18 deg C) iit will blow cold air for a certain amount of time, but then something cuts out and the air is back to ambient temp. After around 30 mins it might go back to blowing cold again, but its fairly random when it happens or for how long the cold A/C lasts.
Have tried fiddling with the A/C on/off button when the air is not cold and you can hear the air compressor rev up but soon dies down and no change in the air temp. If you just leave it set to Auto it will eventually start blowing out cold again, but this could be after another hour of driving.
I don't think this is a gas pressure problem (but I could be wrong) as when its blowing cold, its really cold. I suspect its some kind of sensor with an intermittent fault thats failing to trigger the air con compressor to activate properly.
After the last regas service it worked fine for a few days, but again started cutting out. I no longer work near the garage so did not go back to them.
If anyone has any idea what could be wrong here (gas, switches, sensor, loose connections?) please let me know your thoughts. I will try taking it to another garage and see if they can do some fault finding, but the chances are it will be working when they test it.