Can I ask a BMW question ??

[Pdwight]

A good friend of my wife and I has a 128 (2012), I always change her oil for her as she is a very good friend. Her car has 80K miles and has a horrible squeal when running, I though not too hard so I installed new Gates Idler pulley and tensioner pulley...same squeal. It does not change with the AC on or off...so I am thinking alternator ??

Not much else except the water pump and not a leak from that. I put a large screwdriver against the alternator casing and put that against my ear and I can hear a rough sound as the car is running but not the squeal through the screwdriver....but you can sure hear it outside....any thought ....alternator is pricey and I am trying to help her out.

Thanks

Dwight