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  1. #1
    FEP Member
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    Default Shorted Alternator Field Windings?

    Been having dead battery issues over the past couple days on our 86.

    Battery is only a couple months old and tested good after a charge. I put it back in today and hooked up my multimeter in series with the negative cable and checked for a draw. I’m seeing around a 3 amp draw.

    First thing I did was disconnect the field wire from the back of the alternator and the draw went away. Checked for continuity between the field terminal and ground on the alternator and I have continuity.

    Shorted field/bad alternator, correct?
    I’m a little rusty in my diagnostic skills, but that’s what I seem to remember. Just want to make sure I’m not missing anything else before I drop money on a new alternator.


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  2. #2
    FEP Senior Member BMW Rider's Avatar
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    Oct 2014
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    Calgary, Alberta, Canada
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    Default

    The field should ground. The regulator is what controls the field current. It should be shutting it off when the car is off, thus I'd look at replacing it not the alternator.

  3. #3
    FEP Super Member erratic50's Avatar
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    Dec 2016
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    Nebraska
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    Default

    86+ does not have separate regulator. It’s in the alternator. So the alternator is the problem if the draw is gone when the alternator is unplugged

  4. #4
    FEP Member
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    Default

    Quote Originally Posted by erratic50 View Post
    86+ does not have separate regulator. It’s in the alternator. So the alternator is the problem if the draw is gone when the alternator is unplugged
    There is a regulator on the fender apron under the starter solenoid. I’ll be checking that today


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