[R129 SL] Electrical problems

[Peter Shelton]

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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