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Thread: Alternator not charging

  1. #1
    Member
    Join Date:  Sep 2019

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    Alternator not charging

    Hello, it has been a while since posting. I have made progress since my last post. I have the brakes all done, wheels powder coated and new rubber on.The car starts every time, still a slight issue with exceleration. But the reason for posting, is during the getting it to start trial and error over the last year, I knew the alternator wasnt gnerating, but wasnt a concern. It is new. The plug that came with it, had 2 wires, and the plug and connectors melted when it was hooked up. Fast forward to this weekend. I didnt get a plug but picked up connectors that would hook up to the prongs on the alternator. Using the location form the plug, I hooked up one wire to the bigger terminal, assuming this is the exciter one. Connected the wire to the hot wire in the wirind harness. Started the cran and voila the alternator gauge moved over 13 to maybe 14 volts the lights perked up and then the gauge returned to its normal reading of where the battery is and no more charging. The battery is brand new, and as i said the car fires right up. I recall the alternator charging for a short time last time as I could here it working, but qas I said it was for a very short duration. I didnt hook the second wire as I believe it goes to the gauge???

  2. #2
    Senior Member
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    Does your battery warning light in the instrument cluster work? It must work or the alternator will not. And the bulb canít be an LED. It must be the old fashioned incandescent. Test the warning light by turning the key to accessories but donít start the engine. You must see that light come on to allow the alternator to charge.


    Sept. 81, auto, black interior

  3. #3
    Administrator Ron's Avatar
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    +1

    The large brown wires go on the main terminal. They have 12V at all times.
    The small brown wire with a yellow tracer/stripe goes to the terminal marked "L" (Light) or "F" (Field). It has 12V when the key is in the "Run" position.
    The small solid brown wire goes to the remaining terminal on original units. It has 12V when the key is in the "Run" position. It is usually not needed on rebuilt or replacement units...
    Most auto parts can test the unit if you pull it off (FREE).

  4. #4
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    Join Date:  Sep 2019

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    Quote Originally Posted by Jonathan View Post
    Does your battery warning light in the instrument cluster work? It must work or the alternator will not. And the bulb canít be an LED. It must be the old fashioned incandescent. Test the warning light by turning the key to accessories but donít start the engine. You must see that light come on to allow the alternator to charge.
    Thank you, I never noticed but the battery light does NOT come on, is it likely bad bulb or could there be another cause? And is it neccesary to remove the dash to change the bulb?? Thank you for the help.

  5. #5
    absotively posilutely bytes311's Avatar
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    I had a similar problem where the battery bulb wouldn't come on with the key in the "run" position. It turned out to be a faulty voltage regulator on the alternator.

  6. #6
    Administrator Ron's Avatar
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    +1

    No Battery Light is usually: Alternator's Internal Regulator or Rotor, Bulb, Fuse #5 (oil, brake, etc lights will not work either), Brown/Yellow wire (12V), wiring.
    The bulb can be changed w/o removing the dash by someone with small nimble hands, but very difficult.

  7. #7
    Delorean Guru
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    That light can fail to light during start-up for a few reasons;
    Faulty wiring/bad connection to the flexible circuit board in the binnacle
    Burnt out bulb
    Damaged/burnt wiring to the alternator
    Defective voltage regulator in the alternator
    First thing to do would be to test the wiring and bulb. Disconnect the N/Y (brown/yellow) wire going to the alternator and ground it. Turn the key to the run position. If the light does not light up trace it back to the binnacle and test it there till you find the problem. If the light does work, pull the alternator and have it tested.
    David Teitelbaum

  8. #8
    Administrator Ron's Avatar
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    +1 !

    FWIW- Check the light for a faint glow, including when the key is off...

  9. #9
    Member
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    Quote Originally Posted by David T View Post
    That light can fail to light during start-up for a few reasons;
    Faulty wiring/bad connection to the flexible circuit board in the binnacle
    Burnt out bulb
    Damaged/burnt wiring to the alternator
    Defective voltage regulator in the alternator
    First thing to do would be to test the wiring and bulb. Disconnect the N/Y (brown/yellow) wire going to the alternator and ground it. Turn the key to the run position. If the light does not light up trace it back to the binnacle and test it there till you find the problem. If the light does work, pull the alternator and have it tested.
    Thank you for responding I bit the bullet and pulled the binnacle, and sure enough bad bulb, also when I reconnected the main plug my tach now reads correct. Put new bulb in and alternator works.

  10. #10
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    Quote Originally Posted by Ron View Post
    +1 !

    FWIW- Check the light for a faint glow, including when the key is off...
    Bad bulb, thanks. might consider changing the other bulbs while it is out to LED.

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