Whining under the hood when A/C is on. Whining stops when A/C is off. Suggestions?

[BiggerestAl]

Hello everyone,

I have a 1997 BMW E39 528i. Recently I noticed when I have the A/C on I get a whistling/whining sound like a failed bearing in the A/C belt section of the car. I already replaced the pulley on the alternator belt side so I know what a failing bearing sounds like. I havn't gotten a chance to get underneath and check it out. Is there a bearing that I can replace that is part of the A/C belt? Does anyone know the issue? Also, it does not have to be full bar A/C on display. The sound is constant if there is one bar to maxed out bars. Just to reiterate, the sound goes away when the A/C is completely off, but starts whistling as soon as I turn on the A/C. The A/C still works great and gets cold. Any ideas or help is appreciated.

EDIT: Looking under the hood I noticed the sound only happens when the compressor clutch is activated when turning on the A/C. This leads me to believe the compressor clutch bearing has worn due to age. Does anyone know the dimension of the bearing for my car model and year? I can't seem to find it anywhere!

Thank you