This is a great Illustrated post on Auxiliary fan repair.
Even though it's on the W123 body (I'd venture a bet that the W124 Fans are
similar...I've never been in there,Yet)
http://www.peachparts.com/shopforum/showthread.php?t=98493&highlight=Bosch+Aux+Fan+Bearing%2FRebuilt+123+Body
i-osprey,
You heard correct, "Bad Bearings increase drag and force the electric motor to
draw more (Excessive) Amps"
And as you'll read in Tom's DIY the Bearings are usually the Culprit.
(Especially,if they're the Non-Sealed type!)
Almost the same situations as the Blower Fan Motor.
(Except It has REALLY Cheap Bearings!)