Window Wiper Issue W123

_____ Hello All,
Subject car is 1985 W123 300D turbo diesel. Problem is window wiper suddenly stopped working on a) intermittent, b) low speed. Now it only works on high speed, and does not park in
the usual wiper blade position.
I searched the iNet and this group, but found little of significance. Schematic in Haynes Repair Manual is too small to read.
Solution tried so far is to replace motor with known good one. This did not solve the problem. Could the interval timer relay be responsible for the observed behaviour?
Does anyone have a large schematic to help with diagnosis of the problem?
I know where to find the relay behind the instrument cluster. Can someone confirm what the colour and size is, plus the Mercedes part number?
If you have schematics, please send to "con_trx at shaw dot ca".
Thanks in advance.
/ John
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Via email, he has discovered it is his combination turn/wiper stalk is bad. Broken wire.
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wrote:

Correct. There are 6 wires that emerge at the bottom of the hollow stalk. They are soldered to connections on the switch body from which colour coded wires go to the 12 pin plug in a harness that carries other switch wires as well. When the stalk is moved when you signal left or right, or move it when blinking the headlights, or go to high beam and back to low beam, those six wires are bent or "flexed" a bit. After many years of "flexing" the copper and insulating materials become brittle, and eventually break.
I was able to replace a broken black wire. The break was directly at the bottom of the stalk, and only 3 mm were sticking out. This was just enough to solder a new black wire on it and solder the other end to the connection point on the other side of the switch. A red wire showed signs of almost breaking, but i decided to leave that one alone for now. The switch itself looks to be very well made. However, the major point of failure is the set of six wires that go from the stalk to the connection point on the switch. If the individual wires of the six cannot be replaced, them the only solution is to get a good used switch, or a new one.
Removal of the stalk and switch is simple. Installation is a bit tricky because you have to line up the mounting holes exactly with the tapped metric 3 mm holes on the steering column mounting bracket. A long tapered centre punch was a great help.
Once the black wire was repaired, the window wipers worked fine again on "intermittent", low spped setting, and high speed setting. The wipers also parked again as they should.
/ John
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Thanks for the updates John and Tiger. Will likely be a big help to me someday as I plan to keep my W123s a long time!
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replying to <jch, Tim wrote: Thank you for posting your experience! Just got a gorgeous '84 300D (4th Benz diesel in the 'stable') with the same problem described. I was 2" from ordering a wiper relay, and popping out the inst. cluster when I found this post. Sure enough- broken black wire! A very easy fix!
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