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Air Suspension Problem

Discussion in 'Model S: Driving Dynamics' started by Butcher, Jun 14, 2015.

  1. Butcher

    Butcher Member

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    I have an S85 with air suspension. Last week I noticed that the rear of my car sat crooked. The driver's side rear was lower by ~3/4". I tried lowering and raising the car to see if it would readjust itself, but it actually made things worse, the front actually raised it self higher than usual on the normal setting, not much but enough to notice it, while the driver's side rear still sat really low and crooked.

    I took the car to service yesterday, they said they readjusted the limits on all the corners and that fixed the issue. The car was nice and even on all corners. Today, I'm parked in Low setting, I change it to Normal to get out of a driveway and I feel the front raise and the rear starts raising and stops. I get out and sure enough the driver's rear corner is again lower and the car is sitting crooked. This time it's not as drastic, it's off by ~1/2" and the front height seems correct.

    Has anyone had this or seen this? I've been searching but haven't found anything.

    The car is updated to the latest software version.
     
  2. tomas

    tomas Traded in 9 rep bars for M3, used to be somebody!

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    Never seen it or heard of it on this forum over 2.5 years. Seems you've got a faulty corner... something sticking. If it hasn't been on the forum, it probably has no TSB, so service center may try everything else to eliminate any other causes before replacing. Best would be if you could show them as it happens. Is it consistent enough that you could raise then lower at the Service Center to demonstrate?
     
  3. Butcher

    Butcher Member

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    It just happens the one time and then it just stays low in that corner. I changed the height a few times when I picked the car up from service yesterday and it was fine, I changed it today and it failed. Nothing I try resets it, so all the service guys see is the end result.
     
  4. woof

    woof Model S #P683 Blue 85 kWh

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    I have exactly the same problem. I had the service guys look at it once and they did some adjustments. When it came back I didn't get to see it as I wasn't home, but the next day it was back to being off kilter when parked in my garage. I've tried to determine if the garage is off level or something, but haven't been able to find any indication. I never bothered to report it after that...it doesn't seem to have any effect while driving.
     
  5. Butcher

    Butcher Member

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    Is yours low on the same side (driver rear)? I can feel the car pushing me around in different directions when I'm driving on the freeway. Like it has really bad alignment, also the rear tire rubs on the fender liner when I go over big bumps or I have people in the back. I'm going to get service to look at it again ASAP.
     
  6. lolachampcar

    lolachampcar Active Member

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    Just a guess but I would say it was a fault with the mechanical linkage between the position height potentiometer or the pot itself. I base this on (1) the air pump would run a lot if there was an air spring leak and you would likely get a Maintenance Indicator Light (MIL) when the corner did not reach the assigned height within a specified period of time and (2) the SC reset the corner heights and it was ok for a short period of time. Given that the SC has looked at the car for this specific problem, I would think they would have throughly investigated the mechanical linkage question and thus I would lean more towards a bad pot.

    You can set the car to max height and look at the pot linkage either over the top of the wheel or through the spokes. I might simply be easier to ask the SC to replace the position sensor and re-calibrate ride height.
     
  7. Butcher

    Butcher Member

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    Thanks, I will bring that up to them tomorrow.
     
  8. AudubonB

    AudubonB Mild-mannered Moderator Lord Vetinari*

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    Nice troubleshooting, Bill. Two questions:
    1. Can you re-write this, because it seems to me that after the "between..." you're missing an "...and the XXXX":
    ; and
    2. Are there four potentiometerss, one for each corner? Surely there can't be some mechanical spider between just one of them and all corners???? :confused:
     
  9. lolachampcar

    lolachampcar Active Member

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    Sorry about that. It was an awkward attempt on my part to explain the term "pot" which I routinely use for potentiometer.

    Basically, just check the physical link between the small screw in ball joint on the upper suspension arm to the ball joint on the potentiometer arm.

    There are indeed four position sensors, one for each wheel. If it is like the Mercedes system, one side will report a rising output voltage on raising while the other side of the car will report falling voltage.

    Here is some data from a suspension lower module I did for one of the MB tuners-
    New Page 1
     
  10. AudubonB

    AudubonB Mild-mannered Moderator Lord Vetinari*

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    I'm into dead horse flogging here, so I think what you were saying is "...between the position height SENSOR AND the pot itself." That makes sense even to me. Before you had the pot going to the pot and....oh, black-kettle it all.
     
  11. woof

    woof Model S #P683 Blue 85 kWh

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    It's actually more like it's HIGH on the passenger's rear, while the driver's rear seems normal. The passenger's rear seems high by an inch or more. I don't feel it (or notice it at all) while driving. Seems only an issue when parked.


    Left (Drivers Side)
    Left.png

    Right (Passenger's side)
    Right.png
     
  12. linkster

    linkster Member

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    #12 linkster, Jun 14, 2015
    Last edited: Jun 15, 2015
    Wow. There certainly are variances in body fitnent, but not THAT much. Measuring from the ground to the top of the wheel arch/opening is really not an accurate method but certainly can be an indicator. Have the SC drive your S onto the alignment rack where they can measure/verify (SB-13-34-003) an accurate ride height from the four corner subframe bolts (the same bolts that they measure from to insure a proper level ride height before performing an alignment). Like champ already stated, it's probably a faulty ride-height sensor or linkage issue. I am guessing that it's not an intermittent wiring/connector issue in that a trouble/fault warning/code would most likely appear.
     
  13. wannamodels

    wannamodels Member

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    Siily noob question: could this just be the "automatic ride height" adjusting? If this only does this when parked does that ride height feature make the car "level" by extending right rear? just curious, sorry if that was mentioned.
     
  14. Butcher

    Butcher Member

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    No it sits crooked on flat ground.
     
  15. Butcher

    Butcher Member

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    So the car has been in the SC since Wednesday. Still no word on what's wrong or what they are doing to it, but the service rep said that engineering people were involved. She also mentioned that there was another car there dealing with the same issue.
     

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