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alternator wiring question?

Discussion in 'The Garage' started by 85m1009, Sep 20, 2005.

  1. 85m1009

    85m1009 1/2 ton status

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    I am looking for someone to explain how to wire up a factory alternator. I am building my entire wiring harness and can not figure out how to hook up the two wires that plug into the alternator. I know that one wire normally feeds through the check engine light but I am usure the exact circuitry or if it is even necessary for proper alternator function.
     
  2. dremu

    dremu Officious Thread Derailer Premium Member

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    #1 goes to the alternator light. The far side of the light goes to hot, prolly with the key on, and the #1 wire goes to ground when the alternator is NOT charging.

    #2 must be hot for the alternator to ... err, it's the field, or something, so it has to be hot for the alternator to do its thing. Have it go to the ignition hot and you should be fine.

    You can, I gather, run #2 directly off the big wire, making it a one-wire alternator, but I would imagine the battery would discharge eventually doing this.

    The #'s given above should be cast into the alternator; if yours isn't, lemme know and I'll go look. I think #1 is the left one looking at the back of the alternator.

    -- A
     
  3. Dallin

    Dallin 1/2 ton status

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    #1 goes to the warning light then to a ignition hot source

    #2 is the sense wire and should go to the main 12V buss or the battery positive terminal or the alternator output post. I listed those in order of best to worst. This wire will not drain the battery if hooked up to any of these postions.

    The #1 wire can drain the battery if it is not switched off with the ignition.
     
  4. ntsqd

    ntsqd 1/2 ton status

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    I've frequently wired the No. 2 wire directly back to the Batt. stud on the alt. No issues there. Never been able to figure out why GM ran that wire to a battery source some distance away when they could have wired it internally in the Alt.

    The No. 1 wire terminal needs a light btwn it and an IGN-on source. This wire 'excites' the alt's field. If it is on all of the time you'll have a draw that will discharge the battery.

    FWIW, you can buy that plug as a repair part, no need to cut it off an old loom unless you want to.
     
  5. dremu

    dremu Officious Thread Derailer Premium Member

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    Acha, I stand corrected; #1 is the one that needs to be hot for the alternator to do its thing... thanks guys! I learn something new every day, and now feel compelled to go fiddle with my homebreew generator again :haha:

    -- A
     
  6. ntsqd

    ntsqd 1/2 ton status

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    oh-oh, wait! Double check that! I typo'd No.s 1 & 2 from your post. I think I'm right, but not sure. I always go by the wire size and not the terminal number. Small wire is the exciter, bigger wire goes to the batt terminal.
     
  7. Dallin

    Dallin 1/2 ton status

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    Number 2 is the sense wire. It allows the alternator to increase its output to compensate for the voltage drop between the alternator and wherever you hook in the sense wire. For example if you hook the sense wire to the back of the battery terminal on the alternator the alternator will try to keep the voltage at that point a constant 14 V. In the cab the voltage may drop to 12 or 13V. If you hook the sense wire up in the cab the alternator will try to keep the voltage in the cab at a constant 14V. The sense wire is a good thing. Hook it up correctly and enjoy brighter headlights. 1 wire alternators are for the show only crowd.
     
  8. 85m1009

    85m1009 1/2 ton status

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    Okay, I appreciate the help, let me get this straight.
    I have two wires to the newer style connector, a brown and a pink with a black stripe. I assume the pink with black stripe needs to be hooked up to a switched hot wire, since every other pink with black stripe needs to be. The brown wire will hook to one side of a bulb and the other side of the bulb will hook to an ignition hot. When the potential on both sides of the bulb equal each other the bulb will go out. UMMMM I think that's it. I figured this out 10 years ago but did not retain the info.
     
  9. dave_90_blazer

    dave_90_blazer 1/2 ton status

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    thats it
     
  10. Dallin

    Dallin 1/2 ton status

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    No, that is not correct. The #2 wire (I don't know what color it is) should not go to an ignition hot source. If you can't figure out where to put it than just hook it to the positive battery terminal. It's the other end of the warning light that needs to go to the ignition hot source.
     
  11. dave_90_blazer

    dave_90_blazer 1/2 ton status

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    he said he has the newer connector, in the original vehicle, the pink/black wire was key on only, and brown was key on through a bulb
     

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