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Thread: T1 charging problem

  1. #1
    Garrett booster
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    T1 charging problem

    84 laser XE just recently got a voice alert about low voltage. Itís actually over charging and undercharging randomly. Iíve pulled the 10 and 12 pin connector on the PM and checked for corrosion. All look good. Iíve checked ground at fender well and checked all connections on the alternator and all were tight with no issues.
    Itís my understanding that the PM controls the voltage regulator on the rear of the alternator. How do I know that the voltage regulator itís self isnít bad and not the PM? Any advice or links to advice would be appreciated

  2. #2
    Supporting Member II Turbo Mopar Contributor
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    Re: T1 charging problem

    You could check the control wire from the PM to the voltage regulator so see if the PM is sending a signal to the regulator. You may also want to clean the case/ground of the voltage regulator as I understand the case is also the ground.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  3. #3
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    Re: T1 charging problem

    Iím not in Ga right now, but when I get back home I will pull the voltage regulator off and clean the contact areas. How many volts should be going between the PM and the Alternator?

  4. #4
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    Re: T1 charging problem

    Quote Originally Posted by Barraguy View Post
    Iím not in Ga right now, but when I get back home I will pull the voltage regulator off and clean the contact areas. How many volts should be going between the PM and the Alternator?
    This will vary depending on the electrical load on the alt. The PM turns the field on and off as needed so the voltage is 12V but since it is on and off your meter will only see "an average". I hope this makes sense... here is a picture of the electronics of 85+ so you can get an idea. Transistor 3 is what is inside for voltage regulator. In 85+ they moved in inside the PM.
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    Last edited by chromguy; 06-05-2021 at 01:12 PM.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  5. #5
    Supporting Member II Turbo Mopar Contributor
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    Re: T1 charging problem

    The voltage on the control pin will be "high" to turn on the ALT field.
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

  6. #6
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    Re: T1 charging problem

    Ok, Iím back from my working vacation and Iím gonna start poking around based on the suggestions and Iíll let you know what I find.

  7. #7
    Supporting Member II Turbo Mopar Contributor ajakeski's Avatar
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    Re: T1 charging problem

    Check the fusible links.

  8. #8
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    Re: T1 charging problem

    Ok I pulled this off and checked the mounting surface. Itís all clean I hit it with electrical cleaner as well. The wire that comes from the PM I removed from the post on the alternator and cleaned that. Alternator works, it will either charge at about 12.2 V or 16.4V
    https://photos.app.goo.gl/VMSb3vff8qJuyGPR8

  9. #9
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    Re: T1 charging problem

    Quote Originally Posted by ajakeski View Post
    Check the fusible links.
    Will the fusible links cause the voltage regulator to not work?

  10. #10
    Supporting Member II Turbo Mopar Contributor ajakeski's Avatar
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    Re: T1 charging problem

    Quote Originally Posted by Barraguy View Post
    Will the fusible links cause the voltage regulator to not work?
    A Failed fusible link will cause the alternator not to charge the battery.

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