Hello. There is a noise in my 2008 XC70, that has been getting steadily more obvious, that appears to be coming from the air-conditioning compressor. My initial fear was that the noise was coming from the transmission, as it sounds like a whine that increases and desreases with engine revs, however, I realised that it stopped when I turned the A/C off. It isn't the fan as the noise doesn't happen when the fan is running without the A/C.

Does anyone know why the A/C in the car would be making this noise? Due to the change in pitch with revs, and therefore the pulley/belt, my sense is that it is coming from the compressor. Does this seem right, and why would it be happening? Is it possible that the compressor simply needs to be recharged, or am I looking at having to replace it.

Any input and suggestions welcome.

Thank you.