The wiper on my '87 300TD is always in the 11 o'clock position when turned off (viewed from behind the steering wheel), i.e. it sits further up the windshield when off than it should.

The wiper works well when needed and wipes all the way to the bottom of the windshield on both sides, but always returns to the 11 position when off or resting between intervals.

Would this indicate that it is installed incorrectly? Or is there an adjustment that can be made while it is installed to move it back a few inches closer to the 9 o'clock position?

Anyone? There is a link in several threads to a no-longer-existing web site that apparently addressed this issue.

Does the whole wiper motor need to come off (as per the procedure linked below) to make an adjustment, or is there a way to adjust it while it is still attached?

https://www.pelicanparts.com/techarticles/Mercedes-W124/53-BODY-Mono-post_Wiper_Repair_and_Replacement/53-BODY-Mono-post_Wiper_Repair_and_Replacement.htm

Sounds like you need to replace it. I don't think there is any adjustment. The position where it parks is determined by an electronic circuit board, sounds like that board has failed.

Really simple. Undo the nut that holds the crank to the motor. Reposition the wiper to the normal idle position. Reinstall the crank and tighten the nut.

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Mxfrank, I don't think that will work. 240ddd says the wiper goes through full movement, but parks at the 11 o'clock position.

It's time for a motor replacement.

__________________
Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission (my only daily driver)

Instagram: @maximed93

You are incorrect. There's absolutely nothing wrong with the motor, since it stops in the same place every time. All he has to to do is synchronize the linkage as I described. It's a ten minute job.

If he just "synchronize the linkage" as you said, the wiper would keep it's current sweep, but park where he sets it. That would cause the wiper to be "offset" from the correct sweep, and it would jam down into the hood, and only come up part way on the windscreen.

If he just moved the linkage, 240ddd would essentially be moving the 11 o'clock park position to the 9 o'clock position.

__________________
Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission (my only daily driver)

Instagram: @maximed93

Again, no. The sweep and position of the wiper is limited by the wiper transmission and the linkage, the not by the motor. The transmission gives the blade its up/down motion, and the linkage determines its angular position.

The motor just spins in a circle. Its only trick is to always stop in the same spot. As long as that spot is synchronized with the blade being in the park position, it all works. What's happened here is that the nut is coming loose and has allowed the link to slip.

Thanks for the feedback. I will try repositioning the wiper as described by Mxfrank and report back what I find.

Good luck. I hope Mxfrank is correct, as I have never seen a wiper system that has the park position controlled by the linkage, but I am not particularly well versed on the W124 mono wiper.

__________________
Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission (my only daily driver)

Instagram: @maximed93

You've clearly never worked on a Mercedes monowiper setup.



Take a careful look at this animation, and pay attention the motor and bellcrank in the first few frames. The motor simply spins, its motion isn't complex. The bellcrank is what causes the mechanism to oscillate. The maximum "left-right" extension is limited by the configuration of the levers, and the maximum "up-down" by the rotation of the transmission and its internal crank. The arm can never move below the level of the windshield. If the nut allows the crank to slip, all that will happen is that it won't stop in the correct position. By repositioning the crank and tightening the nut, you can make the wiper park wherever you like.


https://www.youtube.com/watch?v=HGO8B86PZDg


This happens...a lot...in freezing weather. The wiper freezes to the windshield, and the torque of the wiper motor causes the crank to slip under the nut. When the mechanism defrosts, the wipers won't park in the correct position.

Finally got around to doing this and can confirm that mxfrank's assessment is correct. This is overall a quick procedure. My arm is parking correctly now. Thanks.