Mercedes SL600 with wiring problems

We are working on a very clean and original 1995 SL600 (129 chassis) that has less than 30,000 miles on it. Unfortunately this vehicle was made by Mercedes with faulty wiring insulation that has deteriorated and caused short circuits in many components.  The main engine harness (just includes the fuel injector wires and a few others) is in the worst condition. The main body mounted engine harness has some wiring circuits that are bad, Mostly the air mass meter harness. This harness is over$5000 for the part and approximately 60 hours labor to replace. It runs from the headlights to the trunk of the car, behind the dash and under the interior. This job at the Mercedes dealer could legitimately be $14,500. Just for the body mounted harness. Here at Autobahn Performance Inc. in Ft. Lauderdale Florida we have developed a repair kit and procedure to repair this harness without removal for less than $1800. It will work on V12 engine in the 129 (SL convertible) chassis and the 140 chassis (4-door sedan or 2- door coupe). In rare cases more than the normal wire circuits are affected by the insulation deterioration and the harness is unrepairable. This is usually only in European-delivered vehicles and the sedan 140 chassis. If a wire suffers from insulation deterioration the entire length of wire must be replaced. Trying to splice onto a section of the wire will not work properly and will result in short circuits and possibly a fire. The insulation will start to crumble near where you are trying to repair it and you will probably make your problems worse rather than better.

The throttle actuators (electronic controlled throttle body, TBA Throttle Body actuators): There is one for each side of the engine. (note: the one on the right side of the engine feeds the air into the left side of the engine and vise versa) The actuators have a short wire harness coming out of them, it’s about 14 inches long, that connects to the body-mounted engine harness. These harnesses also have the insulation failure problem. The harnesses are part of the actuators and are not available as a separate piece from Mercedes. The Actuators can be rebuilt and new harnesses soldered into place. Again, do not try to repair these as you will not be able to properly connect new wires to the electrical connector end of the harness. Short circuits in the wiring of the actuators commonly cause damage to the E-GAS actuators (the control units that control the throttle actuators). These also can be rebuilt.

Posted in Mercedes, Repair and tagged , .

8 Comments

  1. Hi

    We want to buy the conductor control unit 722.9 with parts number A0002701700. COuld you supply for us? Plesae reply inform to us teh soon the best.

    Thanks and best regards
    Tuan,Ng

    • We are not allowed to purchase this part at this time, we used to be able to. Beckmann technologies can rebuild them if they are Nag2 or Nag3 that is the next number on the valve body under the part number. They only need the computer plate not the complete valve body.

      Beckmann Technologies, Inc.
      3333 Industrial Drive
      Durham, NC 27704

      Tel: (919) 381-2700
      Fax: (919) 381-2707
      Toll-Free: 1-800-742-1021

  2. We are not allowed to purchase this part at this time, we used to be able to. Beckmann technologies can rebuild them if they are Nag2 or Nag3 that is the next number on the valve body under the part number. They only need the computer plate not the complete valve body.

    Beckmann Technologies, Inc.
    3333 Industrial Drive
    Durham, NC 27704

    Tel: (919) 381-2700
    Fax: (919) 381-2707
    Toll-Free: 1-800-742-1021

  3. Hello! I must applaud your efforts to rescue some of these awesome cars. I first read about the hazards of the bio-degradable wiring after I had purchased a “perfect” 1993 600SEL. My mechanic replaced the water pump and some other spendy stuff, AND was mostly encouraging about the electrics because many of the harnesses were new and could be ID’d by their bright blue connecting ends. I had about $12,000 in that car and was just loving it when last January I was driving to a gas station in my town and smoke beging to rise fron under the transmission hump. The car burned up, a total loss and almost took me with it. Frankly, I want to sue Mercedes for appropriate compensation. If you know an attorney who can help with this I would not just appreciate that, I’d share something from any settlement. Thanks and get your ride fixed before this happens to you! Dan Grinde, Kalispell MT USA pinetreenine3@yahoo.com

  4. Hello! I must applaud your efforts to rescue some of these awesome cars. I first read about the hazards of the bio-degradable wiring after I had purchased a “perfect” 1993 600SEL. My mechanic replaced the water pump and some other spendy stuff, AND was mostly encouraging about the electrics because many of the harnesses were new and could be ID’d by their bright blue connecting ends. I had about $12,000 in that car and was just loving it when last January I was driving to a gas station in my town and smoke beging to rise fron under the transmission hump. The car burned up, a total loss and almost took me with it. Frankly, I want to sue Mercedes for appropriate compensation. If you know an attorney who can help with this I would not just appreciate that, I’d share something from any settlement. Thanks and get your ride fixed before this happens to you! Dan Grinde, Kalispell MT USA pinetreenine3@yahoo.com

    • Did you ever get satisfaction from mercedes? I have a s500 and the entire engine harness & excelarator harness as well have decomposed! It almost took me out… I would think this being not a warranty issue, but a flaw in the manufacturing& would lend itself for replacement by mercedes s. Someone will get killed. Who could afford to fix there problem. They actually created a car witch is designed to decompose as you drive… That is wrong and illegal.

  5. Hi there!!! I have a problem very similar to what was stated here ( main engine compartment body wiring harness) it’s biodegrading properties were responsible in a small fire in the engine compartment, burning away the old insulation surrounding the wiring loom including the coating around the wires burning and crusting away. I tried asking Mercedes for a replacement part and they simply said we no longer and will no longer make this part. So I’m stuck between a rock and a hard place…

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