Hi all. Before reading this, to put things in perspective, we Australians sit on the wrong (right-hand) side of the car, in case I may confuse you, I'll try not to.
I've just had a problem develop this afternoon in relation to the windscreen wiper on my 1990 300CE.
Up to today the wiper has been working silently & faultlessly, so I have never had cause to pull it apart.
It was working fine, when suddenly the wiper arm came to a sudden halt on the left side of the windscreen, without any undue accompanying noise. I pulled over out of the traffic, turned the wiper switch off, then upon inspection I found that the tip of the wiper blade had caught itself under the edge of the windscreen trim. When I forcefully moved the wiper down slightly to free it from the trim, it immediately returned across to the park position (in front of the driver), & caught the trim on the drivers side.
I then turned the wipers on & the same thing occured. After freeing it up again I left the wipers off & returned home slowly in the rain.
Once home I removed the wiper blade assembly from the wiper arm & clicked the arm up so it was off the windscreen. I then turned the wiper on and observed how it was functioning. The arm travelled its full sweep & it did its normal out-in-out-in as per usual. It was at this point I noted that whenever the arm was at a the extreme of its travel (ie. at one side of the windscreen or the other) instead of the arm being retracted to its shortest length, it was at about 3/4 length.
Normally the arm is retracted at the end of its travel, thus keeping the tip of the wiper blade from contacting the trim. Furthermore, by turning the key on-off very quickly, & closely observing the arm throughout its arc, I found that instead of retracting when either side of the centre of the windscreen as per normal, it was out of sync, and ended up extending at the end of its travel path, instead of retracting.
I have no previous experience with these monowipers, & after doing a search I found lots of articles on noise, lubrication, transmission failures, etc., but nothing in relation to my problem.
If anyone out there has had the same dramas with their 124 I would certainly appreciate a nudge in the right direction as to how to remedy this situation.
Cheers.

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Marc Whitting
Australia

i believe that the gears inside strip. mine was doing the same thing as yours. drove me crazy for a few days trying to figure out why. i stopped mine in the straight vertical position and pulled it up to it's fully extended position. it now works good, but at the apex, the blade runs over the windshield trim. i guess i pulled it past the stripped teeth. it'll get me by until i can find a used good wiper arm, since these aren't cheap.

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"the simplest answer is usually the correct answer"

1991 190e, 2.6 (helga)
91,000 mi

Wiper transmission is stripped. I think the last time I priced on was $1400

Thank you to Aqua190 & Stan Pittman for your valued input.
Come the weekend, I'll begin an exploratory of the transmission to see the damaged part(s). I wasn't too sure (confident) whether I should tackle this on my own, but if the chances are that it's already buggered, then I feel better about dismantling it.
Once I get to the root of the problem, and can have a good look at it, I'll let you know the outcome.
Cheers.

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Marc Whitting
Australia

i had to pull mine out to fix the park switch in the motor. i never could figure out how to get the big flat black cover (about the size of your hand, where the wiper arm pivots) off the dang thing. i took the phillips screw out, and tired sliding it, tried prying it, finally gave up. is there a trick to it?

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"the simplest answer is usually the correct answer"

1991 190e, 2.6 (helga)
91,000 mi

aqua

You have to lift the cover on the arm, undo the allen bolt, lever off the wiper arm and blade, then the cover snaps off.

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1992 124 E200 (Euro)

Mine has jumped gears twice. I had to move down in blade size so it wouldn't strike the moulding. You may consider doing that instead of replacing the wiper transmission.

The sweep is about 10% less that what it originally was but it works just fine.

Good Luck

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-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi

Thanks for the hint, Paul. I may well try that in order to be able to still use the vehicle (winter over here right now), until I can source & afford another transmission.
Cheers.

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Marc Whitting
Australia

Well, I got stuck ito the 124 wiper transmission earlier this week using some of the excellent postings available on this forum. I've no idea why I was lacking confidence, it really wasn't that difficult.
Once I had undone the linkage, I was able to revolve the working mechanism by hand, and discovered what felt like a coarse spot at the midway position (when wiper arm would be pointing vertical). When I separated the housing, exposing the plastic gearing I found the root of my problem, so similar to other 124 owners.
The round white plastic gear was fine with no damage to its teeth. However it was a different story for the black plastic 'rack' that the white gear arcs around within. The centre section of rack teeth, about 6 in all, had been ground down to almost non existence, hence the coarseness at midway position.
At this point I realised that the small black bits that I'd noticed lying around inside the housing were in fact what was left of these ground teeth.
Any lubrication that had been applied when assembled by Bosch had now turned into a hard wax-like compound, and was only evident on the outside edges of the rack - none where the teeth mesh.
I then undid the 3 screws that keep the clamshell located. The 2 slides were in good shape, as were the steel wheels that run within. But once again the only lubrication was outside of the areas where any friction occurred, and had turned into the hard wax.
I was turning the white plastic gear & watching how the steel rod moves in & out of its slide - I could feel a little resistance. Out of interest I applied just a little WD40 to the shaft & slides, just to see what difference lubrication would make. My God, it was night & day - smooth as & no resistence.
The bottom line to all this is that I have to pay AU$200 (US$150) for a 2nd-hand wiper transmission from a local dismantler.
I will be dismantling the replacement & thoroughly lubricating the appropriate parts - not exactly sure what grease to use...I heard that white lithium grease may do the trick...anyone have any ideas?
Having performed this removal/dismantle of the wiper transmission, I cannot emphasize too highly the importance of checking out your lubrication - ok, you have to set aside several hours to do it, but it would be well worthwhile.
Cheers.

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Marc Whitting
Australia

you found exactly what i found in mine. fortunately, i located a used one also that seems to be good.

__________________
"the simplest answer is usually the correct answer"

1991 190e, 2.6 (helga)
91,000 mi