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Thread: How to test the alternator

  1. #1

    Question How to test the alternator

    What is the best way to test the alernator for proper output. My batteries are not recharging. I looked in the manuals and could only find how to remove and replace the alternator. I must of missed something. (Stock motor)
    1969 M715 W/WN

  2. #2

    Default

    Go buy a cheap volt meter and set it for 24 volts DC. Ground the correct lead and place the positive lead on the output terminal. It should be at least 24 volts.
    You may have to adjust it. Adjust to the tic mark on your gauge and check final voltage with the meter.
    Liz, covid, murdered 10/19/21

  3. #3

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    There's a small pipe plug towards the pully end of the alt body. Remove it to gain acess to the adjustment screw. With the voltmeter attached, turn the screw till you get 28.8 V output.

    If you can't achieve that, the alt may be bad.
    This post is closed-captioned for the hearing impaired.

  4. #4
    Join Date
    Dec 2006
    Location
    Springdale, Arkansas
    Posts
    1,431

    Default

    If all else fails, just wet two fingers and...ooops, sorry wrong thread.

  5. #5

    Default

    how old are the batt's. a bad battery will never recharge, thats first, then ck your output voltage and its best to see the amperage output also you can show good voltage but if the amperage wont come up the alt isnt charging even if it shows a reasonable voltage
    68 M-715 MVPA #2710

  6. #6

    Default Done thanks.

    The batteries are new. I adjusted the output, and also cleaned the ground cable to the engine block with a wire brush. Works great now. Thanks guys.
    1969 M715 W/WN

  7. #7

    Default

    FYI - adjusting should be done with a running temp motor and fair conditions.

    Output increases with lower tempertures and vise versa with higher ones. Adjust to 28.8 on a cold day with a cold alt and the output will be low when you get running.

  8. #8
    Join Date
    Dec 2003
    Location
    SF Bay Area, CA
    Posts
    499

    Default

    Quote Originally Posted by adk4x4 View Post
    FYI - adjusting should be done with a running temp motor and fair conditions.

    Output increases with lower tempertures and vise versa with higher ones. Adjust to 28.8 on a cold day with a cold alt and the output will be low when you get running.
    That's some good info, Thanks!

  9. #9

    Default

    The adjustment is very sensitive. Move slowly and in little bits at a time.

    I forgot to mention above that the tic mark on your gauge should be right around 28. volts.
    Liz, covid, murdered 10/19/21

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