Now that you know the problem is an accessory device driven by the belt you need to spend more time testing pulleys to find the one with bad bearings or drag.

You already made two wrong assumptions. Thats an expensive way to find the problem as from here on the parts start getting costly.

Test them.

Spin them by hand, listen, feel and observe. You should be able to locate the offender.

__________________
Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)