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Thread: Alternator wiring help, please

  1. #1
    Join Date
    Oct 2005
    Posts
    147

    Alternator wiring help, please

    I have searched by haven't really found a definitive answer.
    I have a 2001 5.3 in a 92 fullsize.
    The alternator has two wire coming from a weather pak connector.
    One is gray, one is brown, and the brown wire has 9.5volts when the key is on.
    I am trying to wire in my idiot light to the dash, but am unsure where to splice in.
    It appears that the brown wire goes in red 15 on the pcm and a gray wire comes out red 52.
    I have read that it is important that the light be connected for its resistance.

    I have the alternator wire from the original truck dash, but need to know where to hook it in the new harness.

    Thanks for any help
    '92 Fullsize, swb rc
    5.3L/T56 conversion, comp XR275 HR cam .566/.568 lift 222/224 duration 112 lsa, crane dual springs, trick flow push rods, K&N Filter, Nelson Performance tune, Keisler shifter relocation kit, Boyd Coddington Smoothie II 18x8 235/55 up front, 18x10 295/45 out back, 2/4 drop, eaton lsd w/4.56 gears

  2. #2
    Join Date
    May 2004
    Posts
    2,120
    I just plugged the old altenator wire/connector into the new altenator and everything worked fine but it's an F-body altenator but it shouldn't matter. BTW, it should be brown which triggers the light and not sure what the grey does.
    Last edited by NITROUS; 07-12-2008 at 11:02 AM.


    97 GMC, 2002 LS6.

    1991 GMC Syclone #1428

  3. #3
    Join Date
    Oct 2005
    Posts
    147
    Thanks
    '92 Fullsize, swb rc
    5.3L/T56 conversion, comp XR275 HR cam .566/.568 lift 222/224 duration 112 lsa, crane dual springs, trick flow push rods, K&N Filter, Nelson Performance tune, Keisler shifter relocation kit, Boyd Coddington Smoothie II 18x8 235/55 up front, 18x10 295/45 out back, 2/4 drop, eaton lsd w/4.56 gears

  4. #4
    Join Date
    Sep 2007
    Location
    Hutto TX
    Posts
    467
    Yeah +1. The alt warning light is brown, from the alternator into the I/P cluster at pin A3, circuit 25 (BRN.) Third from one end.(in 1991)

    Where is the pinout that you are referencing? Could you point me to it? I have LS1 pinouts online, which appear to be different from the truck ones..and seeing as how *I* have the exact same engine under the knife...yeah
    1991 Silverado ECLB
    LM7-T56

  5. #5
    Join Date
    Jun 2007
    Location
    maine
    Posts
    1,458
    what idiot light are we talking about?
    09 CREWCAB LTZ SILVERADO, 6.2, SIX SPEED, CAI,

  6. #6
    Join Date
    May 2004
    Posts
    2,120
    Here's some 2000 truck pinouts.
    Attached Images


    97 GMC, 2002 LS6.

    1991 GMC Syclone #1428

  7. #7
    Join Date
    May 2004
    Posts
    2,120
    Damn!! you better have some cheaters on to read these!!!!!!!!!!!!


    97 GMC, 2002 LS6.

    1991 GMC Syclone #1428

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