[R129 SL] wiper problems

[Jan Kuylaars]

You can fix this very easy; First disconnect the connector from the wiper
control. Then unscrew the plate on the wiper motor. Under these plate there
are four contact rings and on the plate there are four strips. The strips
have at the end contact points. Clean the contact rings and put the grease
back on the rings. Also clean the contact points and look if they are become
pointed. If so take a file and file the points a little flat. Then bow the
strips so that the points are making good contact when you screw the plate
back in position.

Take out the wiper control unit and dissemble. Take some fine sandpaper and
clean the contact points from the used relays.

Put everything together again and it is fixed.

Jan.
  -----Oorspronkelijk bericht-----
  Van: r129list-bounces at mbcoupes.com
[mailto:r129list-bounces at mbcoupes.com]Namens Peter Shelton
  Verzonden: dinsdag 5 juni 2007 22:53
  Aan: SL Mailing List
  Onderwerp: Re: [R129 SL] Electrical problems


  Hi Rich,

  This happens occasionally and the fault is the electronic wiper control
unit.  Sometimes mine used to stop across the windscreen on intermittent or
low speed, or just not operate!.  On high speed the electronic controller is
effectively by-passed, as long as the electronic unit is plugged into the
loom.  Mine was fixed under a car warranty as this happened 2 weeks after I
bought the car, otherwise I would have had to locate the fault and fix the
unit/ buy another one.

  The controllers are packed with a few electronic components and an SCR
(electronic switching device - a square black and silver thing about the
size of a dime), is the bit that fails.  I still have my old unit for
viewing purposes.

  Hope this helps, Kind Regards, Peter S.
    ----- Original Message -----
    From: Oldbenz1 at aol.com
    To: r129list at mbcoupes.com
    Sent: Wednesday, June 06, 2007 3:23 AM
    Subject: [R129 SL] Electrical problems


    On a recent long hiway trip,  the '92 500SL was exposed to one of its
rare rain experiences during which I discovered some annoying problems.
Wiper switch was intermittent, with the low-speed and interval wiper
settings working only occasionally (mostly not at all).  Fortunately, the
high speed wiper position was OK so I was able to drive safely.  Also, when
signalling lane changes, the cruise control would act up, sometimes shutting
off, other times speeding up as when the cruise lever is moved to the
"Accelerate/Set" position.  When this happened, the warning lights on the
instrument panel would go crazy so I felt like I was playing a pinball
machine- different colored lights flashing everywhere, fuel gauge instantly
dropping to zero, red oil pressure light and seat belt light flickering,
etc.!    This anomaly was seen whether the wipers were on or  not.  I
suspect the combi switch is the culprit, although maybe there is a wiring
harness in the steering column that is at fault.    My question is can the
combi switch be taken apart so electrical contacts can be cleaned?  Failing
that,  is replacement of the combi switch likely to solve these problems?
My concern is the cruise control problem that shows up when signalling lane
changes- it would seem that the combi switch functions and the cruise
control would be two separate systems.
    Rich


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