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Thread: 1 wire gm alternator

  1. #1
    Member JUNIOR BUILDER
    Join Date
    Feb 2006
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    72

    1 wire gm alternator

    i have a 1 wire gm alternator when i start the car sometimes the gage shows not charging sometimes for a few minutes all of a sudden it starts charging can i fix this or should i bring it into a shop

  2. #2
    Senior Member EXPERT BUILDER
    Join Date
    Apr 2004
    Posts
    279
    Those usually are auto turn on. On several of the ones I had, you had to get the revs over 1000rpm for it to turn on, then it stays on regardless of rpm. Depending on your pulley size, you may have to rev it a bit more. But not much.

  3. #3
    Member JUNIOR BUILDER
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    Feb 2006
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    but it didn't do that when i first got it

  4. #4
    Senior Member EXPERT BUILDER
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    Apr 2004
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    279
    I guess you got a defect then. Most parts stores will test it for free.

  5. #5
    Senior Member DYNO TECH
    Join Date
    Feb 2004
    Location
    Leonard, Texas
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    414
    I had a stock unit that did the same thing. Always had to rev it a bit and then it worked fine until the next cold start.

  6. #6
    Junior Member SHOW GUEST
    Join Date
    Oct 2006
    Location
    Massachusetts
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    7
    My one wire does the same thing, you need to rev it up to kick on. I had mine checked and it did the same thing when it was tested he said it was Ok

  7. #7
    This is a commom problem with 1 wire alternators. The field needs 12 volts to activate the field windings to start the charging process. Low engine speed on start up is not enough to start the charging process. reving the engine actually will induce a voltage into the field windings to get thing going. I had a similar problem with my 1962 Ford galaxie with the 406 CID engine. I decided to ad a wire. I connected a 12 gauge wire from the second small terminal on the stater solenoid to the field connection on the alternator. This terminal is used only when cranking originally to provide 12 volts to the ignition coil on start up only. A second triger only terminal is found on most gm solenoids also. You can check with a test ligh. Have someone crank the engine. If the light lights only when crankig than this is the terminal. solves the problem. Yup, it is a second wire, but is only used to start the charging process. Who cares. Good Luck!
    Paul Johnson www.CustomClassicsAndPerformance.com

  8. #8
    Senior Member RACING JUNKIE
    Join Date
    Sep 2007
    Location
    Montvale, VA
    Posts
    1,431
    Quote Originally Posted by zano
    but it didn't do that when i first got it
    Probably just didn't notice it.I didn't.It's normal though.Sucks,but normal
    "The problem with quotes on the Internet is that you cannot confirm their validity"- Abraham Lincoln


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