Interesting remote locking system problem (and fix) on 94 850 wagon..

Discussion in 'Volvo 850' started by Doug Warner, Apr 25, 2005.

  1. Doug Warner

    Doug Warner Guest

    One day, I noticed that the tailgate didn't lock when I locked the
    rest of the doors, via remote, or key. So, I locked the tailgate with
    my key.

    Some time later, I noticed that the remote was NOT locking the doors.
    I could unlock, but I had to lock it via the driver's door key, which
    also locked all the other doors (except the tailgate). The spare
    remote exhibited the same behavior, so the problem was in the car.
    If I used the key in the driver's door, every other door except the
    tailgate would lock and unlock with it.

    Some initial troubleshooting revealed that, if the tailgagte was
    manually unlocked, then the remote would both lock, and unlock the
    car.

    I pulled the tailgate latch assy, and noticed that the seam of the
    plastic motor housing was split open along the plunger side. (arrows
    in this photo:
    http://webpages.charter.net/dwarner2/LockFull.jpg
    I wish I had remembered to phoograph the innards, but the way is works
    is that the motor (in the left side) via reductrion gears, drives a
    coarse pitch that runs up the middle of the plunger.
    The screw engages a sliding block that travels between the plunger
    legs, and carries it up, or down via spring loaded detents. It
    releases it's grip on the plunger at the end of it's travel in either
    direction, so the key lock is free to move the plunger as well.

    At the bottom of it's travel (unlocked), the plunger activates a
    switch, that signals to the central locking relay that it's locked.
    When it's up, an "unlocked" signal lead is grounded instead..

    The casing was split along the plunger side, apparently keeping it
    from actuating the switch properly. When unlocked, it was still
    signalling the lock relay (which contains some logic) that the rear
    door was locked, while the other doors were grounding the "unlocked"
    signal. Receiving both "locked" and "unlocked" signals prevented the
    locking relay from responding to the input from the remote receiver.

    When the tailgate was unlocked, the relay still received mixed signals
    in the opposite direction, but somehow, this didn't prevent it from
    operating.

    I tried gluing the housing with cyanoacrylic cement, but it split open
    again on the first cycling of the remote. So, I re-glued it and
    reinforced it with shortened staples sunk into the plastic with a
    soldering iron, then secured with some more glue"
    http://webpages.charter.net/dwarner2/Stapled.jpg

    I think that the motor had a bit of overrun, and when the drive block
    ran into the stop, the remaining torque worked to split the casing
    open.

    It works fine now. And, I've finally removed the loose tailgate liner
    so I can repair the clip anchor holes.


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    Doug Warner, Apr 25, 2005
    #1
  2. Doug Warner

    Arne C Guest

    I´ve got the very same sympthom on my -96 855, so i´ll try your soluton out.
    Tanks for the inspiration, I´ve just got used to use my key, but i miss the
    remote (hope it´ll work as our cat just dropped it into his waterbowl 2
    months ago :)

    //Gert C Sweden
     
    Arne C, Apr 27, 2005
    #2
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