Loud noise when AC is on.

[rufos23]

I have 2003 530i with ~18000 miles. When the A/C is on I hear a loud noice coming from the engine bay. The noise is on for a few minutes then goes away, only to come on again after a few minutes. Its almost as if the noise only exists when the A/C compressor is engaged. Does any have any ideas on what could be causing this ? Has anyone had this problem before ?

 

[Tom]

Could be low on R134A if the compressor engages often, but regardless there will be some noise when the compressor engages.