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894Re: [bmw e28] Central-locking/flat battery?

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  • ajhbd@aol.com
    Aug 14, 2002
      Tom .
      By experience all BMW central locking operates on a Negative pulse.
      Which means the system is constantly live and triggered by the earth.

      On the E28 if I'm not mistaken the control unit is in the fuse box.

      If you have a doggy wire earthing where it shouldn't this will effect the
      whole system,
      make it work over time and run down the battery.

      I would start by making sure all your connections are clean and check the
      condition
      of your wires as far as you can. Wires will wear especially on the door
      joints.
      Get your door panels off as well. The main control will be in the drivers
      door.
      If you feel down you'll see a group of rubber connectors. Water can easily
      get in
      if there laying right at the bottom.

      If that's all clear I'd trace the wires by colour and make sure you have
      constant
      current in both + & -. (Use a Bulb tester)

      You may have to replace the module in the fuse box. This will be trial &
      error as it might not be the fault. New one's are not cheep, but a re-con or
      a second had one
      can be picked up relatively cheep.

      The system is really simple, I'm sure you'll find the culprit.

      PS: One last thing, get a Multi meter, put it across the battery terminals.
      It should read between 11.5 & 12V. Take the fuse out of the Central locking
      circuit,
      If the meter moves up, start tracing back to find out why. Watch out for
      other
      things on that circuit that may effect your reading as your C/Locking and
      Battery
      problem might not be linked.

      Andy