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More Viano door contact woes

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by Valthesoundman, Jul 21, 2020.

  1. Valthesoundman

    Valthesoundman New Member

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    Your Mercedes:
    2010 Viano V6
    Hi All,

    long time reader, first time poster.
    I’ve read lots of threads on the Viano, but none quite hit the spot of what I’m facing:

    I have electric side doors in my W639 2010 Viano.
    Motors work fine, as does most things.

    The side doors randomly don’t trigger the closure detector, meaning the light stays on on the dash, and the rear central locking doesn’t work.
    I’ve changed both full sets of contacts, and although there seems to be a little improvement, it’s not perfect.

    This problem I believe leads to my second problem: the alarm goes off randomly.
    I’ve read that this can be a failing siren battery, but I don’t think this is the case, as when I unlock the vehicle to stop the alarm, the rear locking then doesn’t work again, and I have to open and close one or the other door, until the dash light goes out, and then it locks again.

    It’s as if the door contact fails, so the alarm believes a door has been opened and goes off.

    Any ideas, suggestions or things to investigate would be greatly appreciated!
     
  2. M80

    M80 Senior Member

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    Joined:
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    Location:
    Derbyshire
    Your Mercedes:
    Viano 639, 651 5sp Auto.
    My diagnosis was a micro switch that senses the lock position within the lock mechanism within the door.
    I never repaired or replaced prior to selling so can't say I definitely found the cure.

    If you have use of the pin out designations at the contact plates let me know. It may have use in your diagnosis.

    I did read that the mechanism isn't over expensive, £140 if memory serves.

    Oh, avoid spraying with WD40 and the likes to free it up, it can saturate the switch and cause the problem rather than cure it.

    Also, I went through the RS catalogue and google searching and couldn't find an obvious replacement. Flippin' shame as I believed a couple of quids would resolve it.
     
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  3. OP
    Valthesoundman

    Valthesoundman New Member

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    Your Mercedes:
    2010 Viano V6
    The lock mechanism was my next port of call, just haven’t had enough time without need of the van to drop the door trim completely to get at the latch.

    thanks for the advice, I was about to douse it with WD40.

    £140 is not much, but still a lot if I need to do both doors, which seems to be the case.

    Will see how I get on, WD40 May not work, but contact cleaner could be a first step...

    Cheers!
     
  4. M80

    M80 Senior Member

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    Your Mercedes:
    Viano 639, 651 5sp Auto.
    For future, or other searchers, the plates can be swapped n/s to o/s. Then the pins contact a new area. Tie a lead around the plugs so they don't drop inside the pillar and be a bitch to recover.
    If tempted to clean the pads just use a mild kitchen cleaner to avoid stripping the protective coating.

    It is 'possible' that adjusting the D clips that engage the locks might have purpose, it didn't work for me though.
    Don't be tempted to re align the door, when you start that you'll be there for hours.

    An obvious attempt can be to use a piece of bar, like a Philips driver blade, to actuate the lock while open, it's a 2 position deadlock. But as the door needs to engage the contacts it can't help as the SAM won't see the door closed, or not.
     
  5. OP
    Valthesoundman

    Valthesoundman New Member

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    Your Mercedes:
    2010 Viano V6
    Yes, I swapped out all contacts, receivers and spring pins.
    The old ones had clearly been scratched with a sharp object, and oxidised within seconds.

    Again, for future searches, the plate contacts are an easy swap, but the actual sliding door spring mounts require removing the door trim, or at least the best part of it.

    I’m still surprised that the “state” of the door, ie the contact, whichever it is, is changing by itself, causing the alarm to go off.

    You don’t have have a part number for the actuator / latch mechanism by any chance?

    Thanks!
     
  6. M80

    M80 Senior Member

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    Your Mercedes:
    Viano 639, 651 5sp Auto.
    No sorry, no part number.

    When a switch becomes faulty it can be due to carbonising of the contacts, they are then unreliable rather than just plain u/s. If the failure were mechanical, a spring for instance, the permanent faulty state is easier to diagnose.
    The adjustment of the D clips can be useful for elimination, and not overly difficult to reset later, but consider drawing around the base with a permanent marker.

    I blame the failure on useage rather than age, as so many of these are ex taxis that fits.
    Also the mileage being corrupted can mask the true amount of use it might have seen.
    Mine showed approx 150K miles, actual I believe to be closer to double.

    Feel free to cover your ears but an MOT history check 'might' show date discrepancies that demonstrate that type of usage, especially if it has spent time in London where the MOT's are 6 monthly.
     

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