My 02 TDI has started to make a whining noise which increases in pitch with the revs, but only when the aircon is on. The aircon has also started to make hissing noises now and then, no idea what it could be, anyone else had this happen?
The whining noise will prob be a bearing on it's way out in the AC compressor. if it still blows cold air just turn the tunes up a bit cos it will be expensive to replace.
The hissing noise, if its after you have stopped the car is just the gas/liquid pressures equalising and is normal (high side <> low side pressures equalising. Slight faint whining is also okay when the AC is demanding cooling effort - with my wife's Polo it lets me know that someone has knocked it out of ECON!! There will always be more belt/bearing noises when the alternator and/or compressor is being asked to do work.
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