This was an interesting failure that I don't think has been previously reported.
On my 1988 190E 2.6 one of the two aux. fans would only turn in the opposite direction of normal rotation with some difficulty and made a "ratcheting sound".
The field consists of three permanent magnet segments that are held on the motor frame with spring clips at the ends of the segments. One spring clip was bent up, which interfered with the armature segments, effectively jamming the fan.
DC motors draw maximum currrent at stall, so with insufficient torque to move the fan, the brushes and brush blocks got fried.
If anyone has a used, serviceable motor, I'd be interested. The back of the frame is ink stamped "750" with "118" below. A parts seach indicated that this motor is used on a lot of previous models including 123s, so it's probably fairly common.
If the armature spins smoothly and there is electrical continuity between the power and ground leads, the motor is probably okay.
An archive search on the aux. fans proved very helpful - especially the fact that the fan retention nuts are
left-hand threads. After bending back the French lock tab, I was able to loosen the nuts with a 25/32" (actual size is probably 20 mm) socket on a breaker bar while holding the fan hub from turning with my hand.
Duke
02-26-2011, 12:28 PM
Linear Mode
