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
I know where to find the relay behind the instrument cluster. Can
someone confirm what the colour and size is, plus the Mercedes part
If you have schematics, please send to "con_trx at shaw dot ca".
Thanks in advance.
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.
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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