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Electrical gremlins - any thoughts?

Discussion in 'A6/S6/Allroad forum (C5 Chassis)' started by alanadams, Jan 22, 2007.

  1. alanadams
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    alanadams New Member

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    [Jan 22, 2007]
    My Allroad (2001) has just started giving a weird set of symptoms: When driving, the interior lights fade up and down, accompanied by sounds of the door locks activating. As none of the footwell lights come on, I don't think it's a door switch.
    When I unlock the car, after a few seconds the windows all open. This is not because I'm still pressing the button. This is intermittent. Sometimes they open fully. Sometimes they move down a few millimetres at a time, at about one second intervals. Sometimes there is no problem.
    Pressing the lock switch on the driver's door locks the doors. Often, but not always, the driver's dor then unlocks again.
    After the windows have opened, sometimes holding the lock button on the key will close them, sometimes it doesn't. The door locks make noises occasionally too.
    When the car is locked, it behaves itself.
    I suspect the wiring loom between the drivers door and the dashboard area. Partly I suspect this because I have had problems with it on previous Audis, partly because broken and shorting wires on the door controls could be the cause.
    However, I've taken the door panel off and checked the loom, which looks OK. There was an increased amount of activity from the windows and central locking while I did this, but I couldn't tie it down to movement of the loom.
    I took the lower dashboard panel off. Again moving the looms about might have increased the activity.
    Has anyone else seen anything like this? Is it likely to show up on the diagnostics? What do you suggest I try next?
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  3. evomaster3000
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    evomaster3000 Member

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    [Jan 22, 2007]
    hmmm no expert by any means here, but sounds like maybe a water leak problem shorting circuits......somewhere? sorry not much help but known to do similar on ford galaxy.
    maybe check the scuttle pannel, i think that has a box for the ecu? or something electrical in it, maybe a leak in there shorting things out.
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  4. SteveS
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    SteveS S6 avant

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    [Jan 23, 2007]
    i had similar trouble on a W reg A4. i later read that there was a 'comfort ecu' under the seats that controlled int lights, locks, windows, ect and it gets water in it causing random faults. they said the carpets are so thick you can have nearly 2" of water on board and not know. it was in audi driver mag.
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  5. Caesium
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    Caesium My BM is fixed!

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    [Jan 23, 2007]
    If water is getting in you can noramlly be pretty certain its coming from above and running down as opposed to coming in through the floor (unless there is a bog hole in your floor) check all the drain holes on the bulkhead, these tend to get full of leaves and then overflow into the car.
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  6. alanadams
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    alanadams New Member

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    [Jan 23, 2007]
    The saga continues. The local specialist garage agreed with your suggestion - water in the comfort ECU located under the carpet in the front passenger footwell.
    I stripped out the foortwell side panel and carpet, and discovered no water, and no evidence that there had ever been water. Opening the ECU box showed a clean and dry interior. (What a stupid place to put electronics in a car which claims to be an off-roader!)
    Once again while moving the wiring looms about there was increased activity from the windows and door locks. As before, there was nowhere I could wriggle anything and be able to say "that made something change".
    Summary of symptoms:
    While ignition is on, interior lights flicker, and door locks unlock. Windows don't open
    While car is unlocked, no key in ignition, windows open (all together) at random. Interior lights flicker.
    While car is locked, nothing happens, thank goodness.
    The rear interior light doesn't come on when the tailgate is opened. The switvch is working, because the dashboard display shows when the gate is open. The light works manually.
    All of this seems to be controlled by the comfort ECU.

    By the way - what is the Bosch unit under the back seat - my guess would be the acceleration sensor for the airbags - central location etc.
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  7. Caesium
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    Caesium My BM is fixed!

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    [Jan 23, 2007]
    The sensors for the airbags are normally located under the bonnet or in the centre console between the front seats
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  8. SteveS
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    SteveS S6 avant

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    [Jan 23, 2007]
    might be ABS ecu that you found, audi used to put them under back seat. have you tried a lube and a wiggle of the connectors on the comfort ecu? or any other plugs around the area of trouble in the loom. also have a look at the central locking pump/alarm unit? dont know where it is on yours but its in n/s/r boot on mine, also in a place that suffers water leaks!
    #7
  9. timps
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    timps Shakersville

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    [Jan 23, 2007]
    These are my thoughts.

    The key lock switch in the drivers door lock is faulty the reason why.

    On my A4 I can replicate your cars behaviour :

    If the car is not locked from the outside or by the keyfob then the following happens if you turn the key in the driver’s door and keep it turned.

    1 Door unlocks (if locked from the inside button)

    2 Interior light comes on

    3 After a few seconds widows roll down

    If you lock the car from the outside or by the keyfob this disables the key switch and after that no matter how long you keep the key turned in the door lock, or how many times you turn it, there are no lights or windows going down so when your car is locked this is why it behaves itself.

    Also with my spare key in the ignition I turned the other key in the door lock (quickly twice) and the interior light came on & doors unlock but no widows down.

    So from the above I would bet a lot of money on it being the switch in the drivers door lock.

    Craig
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  10. SteveS
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    SteveS S6 avant

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    [Jan 23, 2007]
    a fair point, worth checking the switch . also the wires from the door lock switch go to the comfort ecu via the bendy bit of loom in the door hinge area where they connect to the car loom. possible break in the wiring/bad connection?
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  11. alanadams
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    alanadams New Member

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    [Jan 24, 2007]
    Could be - Bosch would make sense.
    I'll try the connectors, and also the fuses - intermittent power might cause this sort of behaviour. There's a heck of a lot of connectors between the two front footwells.
    The central locking is electrical, not air, so no pump. Apparently the immobiliser is under the dash somewhere, the rest is done by the comfort unit.
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  12. alanadams
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    alanadams New Member

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    [Jan 24, 2007]
    As I almost never use the key, only the fob, the lock could be the problem. I'll do some experimenting with the key behaviour.

    Thanks for the suggestions folks.
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  13. timps
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    timps Shakersville

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    [Jan 25, 2007]
    If it was me I would just unplug the lock switch & see if the problems persist.

    If it does, then fault could be a worn wire/connector coming from this switch and shorting out & fooling the control unit into thinking that the key is being turned.

    It just seems too coincidental that I can replicate the exact behaviour your experiencing from this switch for it not to be a factor.
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  14. rallye
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    rallye New Member

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    [Jan 30, 2007]
    Hi its worth checking the connectors in the rubber boots that connect the doors to the body of the car. I had similar problems on passat a couple of years ago and it was one damp connector for the rear drivers side door the passat wiring is almost the same as the a6.
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  15. SixAvant
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    SixAvant New Member

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    [Feb 5, 2007]
    Ever find the problem ? Friend has the same problem in his 01 A6.

    His footwell ECU compartment was dry, did find his rear passenger door lock seezed and the drivers door lock did happen to come up as a warning in the diag faults list in a previous service.

    Ponder if its a common fault in the A6's.
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  16. alanadams
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    alanadams New Member

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    [Feb 5, 2007]
    Haven't found anything yet.

    What is is not: not damaged wiring in the driver's door. I've inspected it all, and unplugged most of it - I can't get the plug off the door lock itself, or remove the window mechanism to get to the door lock. There's a special screw I don't have a tool for.
    It doesn't seem to be damage to the comfort ECU, unless there is a failing component. I've removed it completely and inspected thoroughly - no corrosion, no sign of loose components, and on plugging it all back together, it's exactly the same behaviour, so I don't think it's the connectors on the ECU.
    I flexed everything I could reach in both footwells - nothing changed the responses.
    I key locked and unlocked the drivers door many times - it did seem to reduce the frequency of the symptoms, but not by much and could be coincidence.

    It's going in for a service and investigation during half-term. I suspect it will end up as a new ECU.

    He will also be looking for the occasional "ride height system fault" which has appeared on the dash since I first had the car. It's also intermittent, but seems to be related to loads in the rear - not excessive, e.g. two people and two suitcases - coupled with undulations in the road. The diagnostic is something like "improbable sensor reading". Does anyone know whether ten minutes to go from low to high setting while driving is unusual? I wondered whether the air pressure was low.
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  17. alanadams
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    alanadams New Member

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    [Feb 24, 2007]
    The car spent half-term at a specialist Audi-VW shop. The only thing that came up consistently on the diags was "drivers door deadlock" fault, so he changed the door lock.

    After a week of use, there doesn't seem to be a problem any more.

    He also changed the tailgate lock as the rear compatment light and rear-door indicator weren't working. That fault is now fixed. Add a full service, and I thought 4 hours labour was pretty good.

    I now just have the ride-height problem left.
    (new topic)
    #16
  18. Est-in-Swe
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    Est-in-Swe New Member

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    [May 12, 2007]
    My rear door lock was intermittent and then seized to function. This happened a couple of months after a paint job was done on the door. The window and the door lights were ok. Also, if the car was locked and I opened the door, the alarm did not go off.

    Right, the blue connector inside the rubber sleeve, in between the door and the car body, was loose. Connected it and everything is ok now.

    Thanks SteveS!

    A6 2.4 Quattro Avant 2003
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  19. evo08
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    evo08 New Member

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    [Mar 6, 2012]
    Hi, I have exactly the same issues, was it just the microswitch or the door lock?



    #18
  20. crispin
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    crispin Member

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    [Mar 6, 2012]
    2007.......may be too late now.
    #19

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