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If you know ALTERNATORS....Help

Discussion in 'Chevy Trucks' started by owen, Aug 18, 2004.

  1. owen

    owen Member
    from florida
    Messages: 34

    This is for my boat again, so the wire colors may be off......

    early 90's 454, carb.

    My alternator was not putting out a charge. Upon inspection I notice a wire is not connected.

    My wiring diagram shows 4 wires to the alternator. Big orange wire to the battery stud, big black wire to ground, red wire and purple wire go to a plastic plug that connects to the side of the housing.

    The purple wire is turned "hot" when the ignition is turned on.

    The purple wire was not connected….so nothing was telling the alternator to “turn on” and start charging. I connected the purple wire. It charges now, but when I turn off the ignition (3 prong, 3 position) the motor keeps running. There is a purple wire going to the back of the ignition switch.

    A guy tells me to find a different “ignition on” wire and replace the purple wire with that one. I do that and now it charges and the motor now turns off when the key is turned off.

    I can’t believe this was the proper fix. I notice my voltmeter now reads 14+ V when the RPMs are up.

    Am I going to blow up my batteries?

    Am I missing a part…Like a voltage regulator?

    How do I know if this alternator has a built in regulator?
  2. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    All alternators after the early 70's (GM anyways) had internal regulators. Alternators usually charge around 14.7V so the battery can maintain a solid 12V while being used. Don't worry about blowing the batteries unless you see it going over 15V or so.

    I don't know the answer to your wiring dilema though... very hard to diagnose these things without being there. There probably is another wire there somewhere or the purple one has been moved to an incorrect location or something. If it works, seal it up well so it doesn't corrode and enjoy your boat.