I'm new to this forum (but a regular on Ozaudi down under).
I have a 2000 model A4 1.8T which I've owned for around five years. On hot days in our hot Australian summer , the aircon sometimes plays up. Which means of course that sometimes it doesn't, if you're a glass-half-full kind of person.
On a long run when the temp is over about 30C, the aircon intermittently blows hot air, for a second or so, around two to five times per minute. Although it immediately resumes blowing cold air, it doesn't seem quite as cold any more. On cooler days (when you don't need the aircon as much ) this never happens.
I read somewhere (I think on the Bentley's website) that this can be caused by the flaps which control the hot air flow opening spontaneously and admitting hot air into the vents. I remember a couple of summers ago putting my hand up behind the dash on the passenger's side (whilst the car was at rest, natch ) and feeling the plastic actuators on the flap valve move backwards and forwards as the vents gave out hot blasts of air.
The next summer it didn't seem to happen much. I have no idea what's going to happen this year (we are in the middle of spring now).
Life is full of surprises with an Audi
All suggestions welcome.