w124 monowiper problem
 

The monowiper started acting sluggishly, sometimes stopping in mid-stream. So I swapped, one at a time, the fuse, relay, combination switch stalk at the steering wheel and the wiper assembly itself, with known good ones from the parts car. Still not working correctly, whether engine is running or not. Bent the wiper arm to relieve downward pressure. Even switched wiper blades. Battery is good- its starts the car. Any other ideas? I am considering going back in to check the female plug that attaches to the wiper assembly to see if any of the wiring or pins went bad. Oh yes, when I detached the wiper arm, the wiper stub seemed to move properly, and quickly at the high setting; with the wiper arm reattached, its sluggish. Thanks.

mono wiper R & R
 

I don't have an answer. I have rebuilt the mono wiper on my 300TE, and was amazed at how little grease remained inside the head, and that it was dried out and hard. I rec that you dissemble one of the wiper heads, clean and relube, and see if that helps your sluggish problem. It may be that at high setting the momentum of the wiper overcomes the resistance of the dried out lube, but at low setting, the resistance of the dried out lube bogs things down. There may also be a worn area along the track inside the head that bogs things down. The mono wiper from my TE would not retract, and inside the head, the toothed track was totally worn done, literally a pile of plastic dust!

Just an educated guess after dissembling two of these mono wiper mechanisms last weekend.

See the thread below about how th grease the 300E wiper gearbox.

Ditto the previous post - it probably needs to be cleaned and re-lubed. To do so properly, you will need to open it up and clean and then add new lubrication.

See this thread for instructions -

http://www.peachparts.com/shopforum/tech-help/52298-92-w124-wiper-removal-not-cd.html#post307591

This is the 2nd monowiper car I have owned and I do believe that you did a lot of unnecessary work, the assembly needs to be lubed, that should take care of the rpoblem. Worked on my C class and my 300TE

Got the same problema a month ago. the problem was on the internals of the drive system of the monoblade. There is a plastic piece with 3 metal tracks inside the core, this plastic is holded to the metal body by a couple screws.. mine broke two screws and got out from position, & wiper began behaving weirdly, stopping at the middle, just disassemble, use a good bonding glue on the screw holes that's all...
good luck
Igor