Just had the system refilled after 2 years on my 2002 S3. It starts b blowing cool air and then blows slightly warm air from the vents. The pipe on the valve behind the air filter gets cold when the aircon is first switched on and then warms up. I have cleaned the main rad and the condenser some 3 ears ago, when I removed he bumper. Previous to this it worked fine. An ideas?
