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Central Door Lock Relay Burned Out All Lock Motors? 900 1995

posted by  craigo on  Thu Sep 28 07:36 CST 2006
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last visit: Wed Jun 12 05:52 CST 2013
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After all the door lock motors burned out literally overnight in my '95 945, my indy mechanic checked out all the electrical circuitry, but found no problems with either continuity or resistance. I just replaced all the door locks and the relay and everything operates as it should at this point.

Although the relay seemed function during the tests, my mechanic noticed a slight spot of corrosion on the relay's circuit board between the two halves of the relay. His best guess is that, given the right atmospheric conditions, electricity might have shorted, which could have sent a steady current to the motors. This in turn would have fried the motors.

The locking motors in the rear doors and tailgate were very accessible, but the Right Front door (passenger side) is quite inaccessible and normally requires removal of a tightly packed plastic protective housing, as well as the entire latch and lock mechanism; not an easy prospect. Note, the Left Front door has no motor, just a switch inside a case which looks like the motor cases.

While doing this repair, I devised a quick way to remove and replace the motor on the passenger front door without removing anything but the motor itself, which is hidden behind the door panel. If anyone is interested in this time-saving procedure, I'll be glad to write up and post the steps involved.








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    Central Door Lock Relay Burned Out All Lock Motors? 900 1995

    posted by  interstition on  Fri Sep 29 03:21 CST 2006
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    last visit: Mon Apr 28 10:13 CST 2014
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    Hey Craigo,

    One of my 745s hasn't had working central locks since I got it. After I taced it as far as the relay being actuated by the driver's door, I was stumped and stopped trying. But it all makes sense to me now. Even though Aye Roll may be right that the root cause isn't the relay, I will still need to replace my locks if they are fried.

    So if you don't mind posting the "easy" way to get at the front passenger door actuator, I would very much appreciate it. Sounds like a good candidate for the FAQ also.
    --
    Andy in St. Paul - '91 745 218K mi, '91 745 210K, '90 744 189K, all Rex-Regina - past 240s








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      Central Door Lock Relay Burned Out All Lock Motors? 900 1995

      posted by  craigo on  Fri Sep 29 06:09 CST 2006
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      last visit: Wed Jun 12 05:52 CST 2013
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      OK, will write it up and post when I have more time than I do right now.

      Yes, it is a puzzle to find out what the real cause is. I'll continue my exploration and let you know what more I find.








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    Central Door Lock Relay Burned Out All Lock Motors? 900 1995

    posted by  Aye Roll on  Thu Sep 28 09:16 CST 2006
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    last visit: Tue Oct 14 21:08 CST 2014
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    I'd be surprised if it's the relays. Much more likely for it to be the door switch wiring. Either at the key switch or in the harness going thru the hinge, where it flexes all the time. The lock relays were probably just doing what they were told to do.

    The relays lock or unlock doors by grounding one relay control circuit or the other. So it's entirely likely that if a wire is to fail, it will fail touching some other piece of metal, creating a path to ground. I'd guess that this is what happened, and it'll happen again if you don't find it. That driver's door needs to come apart and the wiring harnesses inspected. Find the one that's pinched or getting caught in something, or has bare wires.
    --
    Rob Bareiss, New London CT ::: 92 244-M47-208K ::: Bilsteins, Turbo swaybars, Virgos, Lowered, Group A wing, Tach, 6-Disc, Satellite Radio, Keyless Entry ::: Coming Soon: B-Cam!







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