[R129 SL] automatic gearbox update

[MBKindOfGuy]

BerichtI'vr had an intermittent ASR light every now and then on my 300E.  The culprit in my case has been the coaxial connectors, which in the case of the 300E are in the engine bay.  I've had to clean the contacts, and every-so-slightly bend the center and outer contacts so they make better contact.  It's cleared up that problem.  I don't know where the coaxial connectors are in the SL500 though.

Regards,
Howard M. Ginsberg
1998 SL500, 65KMiles
1993 300E, 132KMiles
1988 300E, Sold at 165KMiles
1986 300E, Sold at 180KMiles


  ----- Original Message ----- 
  From: Jan Kuylaars 
  To: 'SL Mailing List' 
  Sent: Monday, August 13, 2007 6:46 PM
  Subject: Re: [R129 SL] automatic gearbox update


  It is depending on the age of the car. In the beginning the sensors are mounted inside the differential box, that is the part that let your wheels make more turns on the right side than left when you make a curve to the left. If the car has not this  differential box the axes should be damaged after a while because they make different cycles in the curve. By terrain vehicles you can block this to have power on both wheels in mud and sand, but drive on the road without take of the block will damage the axes or the cardan. So inside the cardanbox they can not become dirty, but if there is a failure it cost a lot of labour to replace. The cardanbox and drive axes must be disambled.  Maybe your car has a automatically blocked differential box, what can make the trouble, look in the accessories list in your delivery note ( manual ) 
  If there is a difference in your front wheels against the rear wheels the ASR light and the block will come on.

  So later on mercedes dicide to set the sensors like in the frontwheels ( ABS) on the same manner on the rearwheels. They are mounted near the both axes and the brake disks. Now there is a possebility that they become dirty with small pieces iron, and then they are not counting the cycles anymore. 
  You can take them off and clean the center ( it is a coil with softiron center, mounted near a tandwheel on the axe ) 
  You also can measure the resistance, should be a couple of ohms.  And if the wheels are of the road and turned by hand, you can make a measure with a osciloscope or frecuency counter.  The front sensors often are dirty, and also the cables are sometimes broken with yes and no connection as result. But then the ABS light also goes on. 

  BUT; in the ASR/ABS computer there is software what is calculating with some difference, because that is necessay when you make a curve.
  Only when there is a big difference in cycles between both wheels, the computer reconize that there is wheelslip.

  AND; you said the light comes on after some minuts of having the motor turns without driving. So it cannot be the sensors.

  I believe you must search in the computer itselfs, the overvoltage protect relay, or the instrumentcluster or some wires and/or connectors.
  If some connector is not making contact , the system indicates that it is not safe to drive with the thougt that the ASR will work.
  So the system light up the warninglight so you now you must drive carefully because the ASR system wil not work when necesarry.

  Jan

    -----Oorspronkelijk bericht-----
    Van: r129list-bounces at mbcoupes.com [mailto:r129list-bounces at mbcoupes.com] Namens Oldbenz1 at aol.com
    Verzonden: maandag 13 augustus 2007 18:56
    Aan: r129list at mbcoupes.com
    Onderwerp: Re: [R129 SL] automatic gearbox update


    VERY INTERESTING!  This raises some obvious questions- since I am convinced that my gear 
    box is OK (properly filled, no leaks, no suspicious behavior, maintained better than recommended)- now I wonder the following:  exactly where are these sensors located and can they be tested?   If one or both of the sensors is bad will this cause the ASR light to come on?  Are the sensors expensive and can a do-it-yourself mechanic replace them?  Can this system be disabled without causing other electronic problems?   My rear  wheels are both the same size and I have matching Michelin tires mounted.


    In a message dated 8/12/2007 6:48:47 P.M. Eastern Daylight Time, J.kuylaars at kpnplanet.nl writes:
      At the rear wheels ther are two sensors wich are measure the cycles from both wheels.
      So only if there is a difference betwen them, the computer reacts.
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