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A4 Cabriolet Hood Keeps Opening Up On Its Own - Help Please!?

Springer* Oct 21, 2013

  1. Springer*

    Springer* Member

    Hi there,

    The missus was driving to see a client this afternoon and without warning the cabriolet roof on the A4 decided it was going to open up on its own.

    No pressing or knocking of the release button at all.

    She pulled over and turned the engine off for a few minutes hoping that the system would reset itself and tried again, but as soon as the engine fired and the car did its usual run of sensor checks, the roof opened itself up again on its own.

    I've had a fiddle with it too and it took numerous attempts to get the roof to close again. It would whirr and move a normal for a few seconds and then freeze completely. I'd wait a few seconds and then try again and I'd get a few more seconds of whirring and movement before it would stop again.

    In the end I've managed to get it closed and then intend to remove the fuse while I sort it out.

    Does anyone have any ideas as to what is going on?

    I've seen the various repair guides on this site and I'm thinking its probably something like the dirty commutator thingy, but does anyone else have any ideas?

    As you can imagine I'm pretty worried about the roof flipping up where we're on the motorway at speed and causing serious damage.


  2. hades-

    hades- Well-Known Member VCDS Map User

    with all the rain were haveing id say something is either wet
    or the switch is broke
  3. WOLF

    WOLF Well-Known Member

    hope you get it sorted soon with the weather forecast for this week.
  4. VagPro

    VagPro Active Member

    Hi J,

    I do not think it is a dirty commutator, it is either the switch that is faulty, but even if the switch is faulty the roof should not operate while the vehicle is above a certain speed. Therefore it could also be the roof control unit (not the hydraulic assembly in the boot).

    Have you had the car on VCDS and checked the codes ?
  5. Tolak

    Tolak Member

    I'm with VagPro here; the speed and uncommanded function mean the controller logic is not working correctly.
    His analysis is the basic controller; there is another option of an after market option.
    It is possible that you have a SmartTop installed, which would allow you to open the roof at non-zero speeds, and also interprets the switch position. Worth checking if you have one of those; they can be disabled, or removed easily, to allow you to do basic checks.
    mods4cars product manual has the details of how to disable it, which also lets you know if one is fitted; the installation is behind the trim panel behind the driver's B pillar, so not easy to see. (Not hard , either, but a nuisance for diagnostic "possibilities")
    VagPro likes this.
  6. Springer*

    Springer* Member

    Thanks for the feedback peeps.

    For the time being and with the weather being so awful I've just taken the fuse out for now and that's solved it.

    Yes, the car does open the roof at any speed, which is quite unnerving.

    I'll check out the control unit when the sun comes out again.

  7. Tolak

    Tolak Member

    One other thing; try disconnecting the battery for a while (20 minutes) to allow the roof controller to reset completely.
    If the controllers had got itself confused, a hard reset like this will often clear the confusions. (Applies to all the involved controllers)

    But with the weather hitting the news in the south-west, and heading your way, better not to have random opening happening!
  8. Tolak

    Tolak Member

    Any luck?
    I appreciate with intermittent problems, it takes confidence to put the fuse back in, but for some deliberate around-town testing, it might be useful to start getting more info.
    And have you managed to get behind the trim on the rear panel to see if you have a moisture issue on the controller?
    Good luck.
  9. Tolak

    Tolak Member

    I've been having problems that I've diagnosed as CAN bus problems; as the weather dries out, so the CAN bus problem has cleared, I need to use the VCDS to read the faults and close the loop on that diagnosis.
    But for now, the weather is good, so I can get back to enjoying the car, and have time to add improvements.
    I will also work through all the connectors I can find to seek corrosion or leakage that makes the car sensitive to water.
    Next is to clean the car (and roof) properly, followed by fitting the goodies and repairing the minor issues...

    Still interested in what solutions you have found.

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