Hi All, First post here, got quite a strange air-con problem that I'd appreciate any help diagnosing. Car is a 2003 A4 B6 1.9tdi (engine code AVF). Have just replaced the G65 pressure sensor to no avail. Here are the symptoms: Air con worked last year, but this year was blowing warm. Last year the ECON light stuck on for a while under a wee Had not been re-gassed since I owned the vehicle (5 years) so had system professionally re-gassed using an automatic machine that flushed, tested, lubricated and re-filled. Immediately after the re-gas the air con was still blowing warm air, both when vehicle stationary and under motorway driving. Fuses on box by drivers side door all intact. ECON light off (but goes on if I disconnect the G65 pressure sensor or corresponding 5A fuse). VCDS lite not reporting any relevant fault codes (codes re engine mount and steering angle sensor assumed irrelevant). The first time I checked this a few days ago I got no faults. I thin re-checked and got an "00819 high pressure sensor (G65) 29-10 short to ground - intermittent", so I replaced the sensor with a brand new hella-behr part. Thinking about it I was pulling the fuses to check if the econ light went on/off, this may have been the cause of the fault code. Auxiliary fan not coming on, voltages at the 4-pin fan connector next to the PS reservoir don't change when I switch ECON on/off. No drop of engine revs when I switch ECON mode on/off. Air con compressor pulley seems fine, can't see or hear any problems. VCDS reports a Refrigerant Circuit Pressure of 5.0 bar and a High Pressure Signal (G65) of 20.5% at about 18C ambient temp, which according to VCDS is about right. G65 pressure sensor replaced, fault codes cleared, air con still not working, no aux fan etc. VCDS compressor shut-off criteria: all 0.0 VCDS Compressor torque status: 0, Required Engine Torque: 2.0 Nm A/C valve (N280) current: 0.648 A A/C valve (N280) duty cycle: 62.4% Based on the above I think this means: The aux fan is not the problem. If it was, the air con would still blow cold under motorway driving (as in this thread) The G65 sensor may have been faulty, but now it certainly isn't. The compressor is not starting. According to the shut-off criteria being all zeros, the compressor should be running. A few things I was wondering: If the compressor was faulty, would the aux fan run anyway? According to this thread I suspect the fan only starts if the pressure is above a certain point, i.e. if the compressor is running. How to work out if the compressor is faulty? What other diagnosis checks can I do?!! I'm starting to suspect that it might be the compressor, although I did see another thread about the N280 valve sticking without throwing a fault code. As you can see I have done a fair bit of diagnosis and probably replaced the G65 sensor for no reason, so any help would be appreciated!!!