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Alternator is running, but system won't charge

Discussion in 'Toyota Trucks & SUVs' started by Isaiah, Feb 25, 2015.

  1. Feb 25, 2015 at 10:32 PM
    #1
    Isaiah

    Isaiah [OP] New Member

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    1979 20r Pickup
    I have a 1979 20r that has been having electrical problems for awhile now. First I replaced my battery but my charge light stayed on. The light was still on. Then I got a new alternator and swapped it. Tests with a multimeter says its putting out 14+ volts. As soon as you load the system by turning on lights and the fan, voltage starts dropping and pretty soon its running off the battery.
    Any ideas?? I've read of a 5 or 6 plug alternator? There is a black wire running from the regulator to the alternator area but cannot find what its for, maybe a ground? Any suggestions would be very appreciated!
     
  2. Feb 25, 2015 at 11:00 PM
    #2
    BadBrains

    BadBrains Spreading the Aloha

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    '07 Tacoma TRD OR, '00 Integra GS-R, '75 C10
    King, TC +2"LT, 35's, Aluminum this and that.
    Not sure if it's your problem but double check your ground cable from battery to body.
    On my '83 it went up in smoke from corrosion(The cable, not the truck thankfully).
     
  3. Feb 28, 2015 at 7:53 AM
    #3
    Shadetree

    Shadetree Well-Known Member

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    Locking Tailgate & Gas Cap and extra bed D-rings
    Attached is a general Toyota Charging System document that might be helpful for determining wiring connections. I would first clean the battery posts and terminal lugs and fully recharge the battery with an external charger. Then I would take the vehicle to an auto parts or battery store for a free battery and alternator test to determine if battery and alternator are healthy. They are both codependent on each other.
     
  4. Feb 28, 2015 at 7:59 AM
    #4
    n0rth

    n0rth Well-Known Member

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    Check your regulator, I just went through this with my FJ-40.
     
  5. Feb 28, 2015 at 8:14 AM
    #5
    tomwil

    tomwil Well-Known Member

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    Where?
     
  6. Feb 28, 2015 at 10:55 AM
    #6
    BadBrains

    BadBrains Spreading the Aloha

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    If I still had an old pickup I'd probably convert to a GM one-wire alternator. LCE Bracket

    With that said, you'd probably get better help fixing your current setup over at the Marlin Crawler board.
     
  7. Mar 1, 2015 at 5:15 AM
    #7
    Shadetree

    Shadetree Well-Known Member

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    u
    Sorry, the 833 K .zip file exceeded the TW Forum's limitation. I should have checked the file size first. I have attached a diagram on one Tacoma engine that gives an example of how the charging system is connected.
     

    Attached Files:

  8. Mar 1, 2015 at 6:06 AM
    #8
    Mod

    Mod Well-Known Member

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    stock
    Replaced a alternator and battery on a Geo Tracker last June.

    6 months later, the new-ish alternator would stop charging after 10 minutes of run time and the vehicle would run out the battery and sputter to a stop.

    It wouldn't start charging again until it cooled completely. We surmised the regulator failed.

    Napa lifetime warranty kicked in and replaced the Alt again.

    Do your usual standing voltage check,,then fire it up to see your charge volts,,and then let it idle for a bit. Accessories off at first,,then tested with them on. See what happens. It's a pretty easy and quick check to eliminate a possibility.
     

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