Hi there. I have a 2007 530xi with 107,000 miles on it and since I was the second owner since 94,532 miles, the compressor has always made noise. It's like a moan or a groan but it's just annoying. It is rpm dependent and have ruled out all pulleys. Sometimes it's worse than others. During some hot days, you can tell that it is struggling to cool things off and you will get that smell sometimes. People that know that smell will know what i'm talking about. At this point, I am just really annoyed with it and anyone I take in the car asks me what the noise is and I just respond "Variable compressor Yo."

This is the video.

 

My 06 530 has 171k miles and the AC compressor groans and whines something fierce but seems to work okay. No bad smells (change your two cabin filters if you have not, and/or spray disinfectant spray into the air intake at the filter assembly with the AC on to kill the fungus in the system).

 

totally normal operation. mine does the same thing. Ill tell you what... If thr temp falls below 72 ambient it begins to make that noise all the way down to 32 or lower. Above 72 like summertime, you wont hear the ac compressor at all. ITs WEIRD but normal. Don't worry. And my advice, leave it in auto on 70 degrees year round.

 

Same here. Started to notice it two years ago. AC actually performs great. Annoying in local traffic, but don't hear it at highway speeds. No idea what causes it. No noise at higher summer temps at all.