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Thread: Alternator Not Charging Battery

  1. #1
    Member Midnight Specialist's Avatar
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    Alternator Not Charging Battery

    I recently got my car back from being in the shop for three weeks for replacing the fuel lines and coil overs. After picking up the car the battery light illuminate in ignition position 2 when starting I also get 5 beeps from Dave McKeenís otterstat indicating itís not charging.

    Itís a new alternator from DPI put on in feb. it was working when the car went into the shop. They didnít do anything to the alternator, except put a Alternator Tensioner on it (https://www.deloreandirectory.com/ma...tor-tensioner/). I did notice there was some coolant on the top of the alternator from the coolant line above it.


    The bulb in the warning light was replaced with an incandescent bulb in July when I replaced the other bulbs with LEDs.

    Any one got any ideas on why itís not charging?


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  2. #2
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    Incorrect tension on the belt?

  3. #3
    Motors about after dark Michael's Avatar
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    You need to put a multi meter on the alternator and battery to determine if it's truly the alternator, a break in the charge circut(possibly a wire knocked loose or damaged from the shop) or maybe the dash gauge is just lying to you. Without that info, you are just shooting in the dark blaming the alternator.
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    Member Midnight Specialist's Avatar
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    Alternator Not Charging Battery


    Only blame the alternator because it is not charging based on the dash gauge. Also we ran a multi meter on the battery; no charge.

    If the battery light is not coming on when the key is on position 2 along with the oil light, would that be the reason the alternator might not be charging the battery?

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    Last edited by Midnight Specialist; 06-24-2021 at 10:02 PM.

  5. #5
    Motors about after dark Michael's Avatar
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    Quote Originally Posted by Midnight Specialist View Post

    Only blame the alternator because it is not charging based on the dash gauge. Also we ran a multi meter on the battery; no charge.

    If the battery light is not coming on when the key is on position 2 along with the oil light, would that be the reason the alternator might not be charging the battery?

    Sent from my iPhone using Tapatalk
    If the battery light isn't coming on, then yes you are not charging. The volt gauge reads battery voltage only. It has no idea nor does it care what the alternator is doing. Like I said, you gotta test but based on this new info, start at the bulb....actually look at the back of the alternator and see if the pigtail is secure and intact. If they were doing suspension work, they may have knocked something loose.
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  6. #6
    Senior Member Bitsyncmaster's Avatar
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    A broken charge light circuit could be at the bulkhead connector or the instrument cluster. The connectors at the cluster are often bad after it has been removed. I would start by pulling and installing the bulkhead connectors. Doing that often cleans the pins up a little.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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    Administrator Ron's Avatar
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    Quote Originally Posted by Midnight Specialist View Post
    After picking up the car the battery light illuminate in ignition position 2 when starting ...
    Assuming you meant to say, "... the battery light does not illuminate in position 2...".

    Quote Originally Posted by Michael View Post
    If the battery light isn't coming on, then yes you are not charging. The volt gauge reads battery voltage only. It has no idea nor does it care what the alternator is doing. Like I said, you gotta test but based on this new info, start at the bulb....actually look at the back of the alternator and see if the pigtail is secure and intact. If they were doing suspension work, they may have knocked something loose.
    FWIW, since a mutimeter is reading low voltage, it's probably not the case here, but it is possible for the light to never come on and the regulator kick in (self energizing regulator, high rev, etc). The battery, alternator and gauge are wired in parallel, so the gauge reads both (together), not caring/knowing where the power comes from.

    =====

    I agree that the place to start is the bulb's circuit: Turn the key to position 2 ('RUN' -- Don't start the engine), disconnect the pigtail (Brown with Yellow stripe wire) and tap it to ground (the alternator's casing is a good place). If this makes the light come on, the circuit is OK. If the main terminal reads 12V also, the unit is bad.

  8. #8
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    Have you checked the crimp that splices the GM pig tail to the Delorean wire harness at the Alternator? That butt connector could have come loose or knocked around, that would cause an issue as well.

  9. #9
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    Start the car and start reading voltage directly at the alternator.

    Give 12v directly to the exciter circuit of the alternator and see if it starts charging. (Assuming you aren't reading a charge voltage from the above step)

    (Never have worked on a stock alternator, but according to the schematic it appears to have an exciter circuit, so the above test should be pretty failproof).

  10. #10
    Member Midnight Specialist's Avatar
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    So I changed out the bulb and cleaned the bulkhead connectors with contact cleaner. No light and not turning over now.


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