Audi Repair: Audi A3 1.8 T 1999 A/C problem, coolant temperature sensor, engine coolant temperature sensor

Question
Hi Jan, I own a 1999 Audi A3 1.8 T, and recently the A/C has stopped working. When I turn it on the fan comes on, and the load on the engine increases (idling speed increases slightly), but the air is only supplied at outside temp. Also, for a while now the coolant warning light comes on, even though the coolant level is fine (above min, below max), and now every once in a while the car seems to overheat. Any ideas? thanks for your help

Answer
Sounds like your engine coolant temperature sensor has gone bad, a common problem.  Secondly, the A/C probably lost its charge, the compressor will not kick on if the refrigerant pressure is too low.  I would check those things first,  Let me know,  Jan