I have a 2.8 A4. My AC has worked well up until a couple days ago. Both fans engage while the second fan stays on permanantly (no clue why) my temp gauge in 97degree weather is reading way below the half mark. I figure the motor is cool and that the gauge is telling the truth. Mind you the gauge cluster seems to be working properly with all other gauges. Heres the problem my coolant boils in the reservoir when i turn the car off. Ive checked the cap and the reservoir itself and did not detect any cracks. I have noticed that i have been leaking a small amount of coolant from the radiator.. could this be causing the pressure to drop and be the problem.. and could this have any reason for why the ac has stopped working (i have recently charged the system). AC belt is intact. Not sure if compressor is engaging. yea its a mess

 

It is likely you need a new coolant temperature sensor, it is a common problem, that should take care of the low reading. As far as the A/C goes, I dont think it is tied in in this case. If you just recharged it, you need a VAG COM, or you need to follow this procedure: http://www.audiworld.com/tech/int5.shtml#DiagCodes to check for codes. Depending on what you get for codes, you should connect a gauge to the low pressure side and check the pressure. If there are no faults or a low pressure fault and you actually have low pressure you need to start checking for leaks. Post back with your codes and we can go from there. Otherwise search, theres been alot of threads about this lately.