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Suspension Warning Light 500SL ADS1

Discussion in 'Suspension, Steering & Brakes' started by gfern, Nov 21, 2012.

  1. gfern

    gfern Senior Member

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    Your Mercedes:
    R129 1990 500SL
    Looking for some help please, the car is a 1990 500sl with ADS the suspension warning light has come on. The car has a 16 pin diagnostic and on checking the ADS slot got a reading of 4 blinks, this says acceleration sensor? The only sensors I can see are the ones which also control the ABS and ASR . But in spite of the warning light everything is functioning, ADS fluid level ok, car raises and lowers and also stiffens as it should. The pump is working and I am baffled at this stage any suggestions as to possible causes would be most helpful.
     
  2. WG M-B

    WG M-B Senior Member Authorised Forum Supporter

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    Your Mercedes:
    C63 Wagon in black
    You are right that code 4 is indeed acceleration sensor. They are a common problem with ads 1. The sensor is located on the drivers side front wheel hub. X1 plug and held on by a couple of alen bolts. Mb will order it from Germany as generally its not a stock item.
    They are around £300plus vat
     
  3. Richard Moakes

    Richard Moakes Senior Member

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    Your Mercedes:
    1991 R129.066 M119.960; 2005 W164.175 M113
    There are two acceleration sensors, one on the inner wing under the bonnet and one on the lower control arm. They are different and measure different ranges of acceleration, you need to be sure which is faulty before you spend any money.

    Code 4 is the lower control arm sensor, and code 3 is the body sensor.

    Have you had any recent work on the front suspension? brakes etc..? or hit a large pothole? This can kill an old tired sensor.
     
  4. WG M-B

    WG M-B Senior Member Authorised Forum Supporter

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    You should have x3 wires going to the sensor. 12v +, earth, and signal.
    It is worth checking the power and earth supply with the ignition on to eliminate the wiring.

    You can then do x2 tests to check the sensor. A static test which should see the signal wire providing around 4.5 volts. And a dynamic test which involves pushing down on the front of the vehicle. The signal voltage should change as the vehicle is pressed down

    You will need to recognise the correct pins on the ads ecu first in order to eliminate the wiring. Maybe someone else would have them to hand
     
  5. Richard Moakes

    Richard Moakes Senior Member

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  6. OP
    gfern

    gfern Senior Member

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    Your Mercedes:
    R129 1990 500SL
    Thanks guys that is a great help its sometimes easier when things break and stop things functioning these other faults are so difficult when everything seems to function as it should, its great to tap in to the experience and knowledge on this forum. It does of course beg the question about whether the sensor is that important as everything seems to work, I suppose I won't know till I replace it. And yes the car has just had track rod ends fitted so that fits your diagnostics. Will post the result for other people to refer to. Thanks again.
     
  7. Richard Moakes

    Richard Moakes Senior Member

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    Your Mercedes:
    1991 R129.066 M119.960; 2005 W164.175 M113
    It means your car is locked into the 'firm' setting and will not lower itself automatically at speed.

    If you can live with that, you can save yourself £300+ :)
     
  8. OP
    gfern

    gfern Senior Member

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    Your Mercedes:
    R129 1990 500SL
    Thats good to know, on the basis that I feel nothing wrong the saving £300 sounds good and I never worked out a way of knowing that the car actually lowered itself anyway at speed. The only problem is that knowing something isn't working gets to me so will look at it again in the New Year now I know that it is not urgent. Once again thanks for the help.
     
  9. WG M-B

    WG M-B Senior Member Authorised Forum Supporter

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    It's worth having a good ring around the mb breakers. Although its hard to get ads parts it's not impossible

    You never know your luck :D
     
  10. Richard Moakes

    Richard Moakes Senior Member

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    Your Mercedes:
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    Try Mercman in Hayle Cornwall, I think he might have one of those accelerometers, at least he did a few months back.

    Sent from my Nexus 7 using Tapatalk 2
     

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