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how do i wire a GM 3 wire alternator

Discussion in 'The Hokey Ass Message Board' started by SpeedRacer2002, Sep 30, 2004.

  1. SpeedRacer2002
    Joined:
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    wathena kansas

    SpeedRacer2002 Member

    can anyone tell me where all the wires go??? and i know i can get a 1 wire but i have a brand new 3 wire and i want to use it on this car.....
  2. Brickster
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    Brickster Member

  3. BigDdy31
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    BigDdy31 Member

    Good link man, thanks.
  4. Homeresque
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    Yucaipa, Calif, USA(not to be confused with Yucca

    Homeresque Member

    For the common garden variety Delco 3-wire in a typical non-pigtail hotrod application, do this...
    The big wire(pole with nut) is obviously the power and goes to starter pole, headlight pole, ign pole, whatever, depending on how youre wired. The next two say '1' and '2' and are spade connections. One of them('2' I think) you simply loop over and connect to the big wire pole, thats all. The other one('1' I think) goes to the switched side of the ignition, or you can run to the ign side of the coil, doesnt matter, but must be turned on and off with ign. Now be sure to do this(or once you start the car you cant turn it off without yanking out something), inline on this wire install a one-way resistor, like a zenor diode from Radio Shack so that current can only flow from the switch to the alt.
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  5. Dooley
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    Buffalo NY

    Dooley Member

    I ran mine like this.
    Big wire is wired through my ammeter to the starter.
    In the plug in one, #1 goes to the ignition, the other #2 loops over the the batt post on the alternator.
  6. moondisc
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    Deansboro NY 13328

    moondisc Member

  7. jerry
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    jerry
    ALLIANCE MEMBER

    you can also run a small light buld in line on the wire from the igntion switch. it ahs enough resistance to keep the motor from running on. factory does the same with the idiot light.


    jerry
  8. choprods
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    choprods Alliance Vendor

    Mostly right BUT on that two wire plug in #1 term loops to the back of alt[BATTERY PLUS] with a heavy wire.
    NUMBER2 TERMINAL HOOKS TO ACCESSORY SIDE OF IGN SWITCH-=DONE
  9. moondisc
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    Deansboro NY 13328

    moondisc Member


    [ QUOTE ]
    you can also run a small light buld in line on the wire from the igntion switch. it ahs enough resistance to keep the motor from running on. factory does the same with the idiot light.

    [/ QUOTE ]

    That's how I hooked it up in my 54 Merc.
  10. SpeedRacer2002
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    SpeedRacer2002 Member

    awesome info guys thanks much...
  11. Deville1904
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    Sur Califas

    Deville1904 Member

    Sorry for diggin this thread up from beneath the grave. Just that it seems like everyone seems to have a different suggestion for the proper wiring method on a 3-wire alternator.
    I was running a single wire in my 54 cadillac but that turned out to be very unreliable for obvious reasons.
    So now im looking for a 100 amp plus three wire but I want to make sure I wire it properly the first time.
  12. AllSteel36
    Joined:
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    California

    AllSteel36 Member

    What's posted above is how to "make" a single wire from a 3 wire Alternator.

    Go to madelectrical.com, there's good diagrams...the down side of wiring it (3wire) as a one wire alt, you usually have to speed the engine up to get the alternator to start charging
  13. 65gregg
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    willis,tx

    65gregg Member

    X2 on Mad Electrical
  14. Da Tinman
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    Da Tinman Member

    Any 12v ignition hot can be used on the #1 post, I use the resistor side of the starter, with a diode. Works perfectly.
  15. enjenjo
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    swanton oh

    enjenjo Member

    If you jump the no.2 wire to the batt wire on the back of the alternator, it will work, but you are setting up a chronic low charge condition. The number 2 terminal is used to sense system voltage, and if it is seeing 12.5 volt at the alternator it shuts it down, when the rest of the system may be seeing only 11.8. So it is best to connect that at the junction where most of the systems in the car get their power. the fuse box is a good point, as is a firewall junction. So if you are running a basic system, not many accessories, it's ok to jump the terminal, but if you are using a lot of power, better rethink it.Just saying.
  16. Deville1904
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    Sur Califas

    Deville1904 Member

    This is exactly my point. I am running other accesories and plan on getting it bagged so I really want to wire this properly. Anyone have suggestions on rewiring the ignition. Alot of the wiring in this cadi is OLD =P
  17. DougHH
    Joined:
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    NSW, Australia

    DougHH Member

    I've got a 3-wire from an early commodore in my '59 Belair. It's doing my head in. Car starts and runs fine, but when you go for a decent drive and you shut the car down it will not start again and needs to be jumped, which will also not happen for a while after stopping. I've also got no dash lights anymore and dim headlights after converting to Halogens which is driving me nuts.

    Multimeter is telling me its running 13 and a bit volts or there-abouts to the battery when cold.

    i've been through 3 alternators so far trying to rectify. one was confirmed stuffed by an auto electrician. last one i bought which should be good was a wreckers reco one.
    I've run the Big pole to the battery not sure which one was to the generator indicator bulb in the dash and the final to the relay/switch that runs to the horn.

    Can anyone please help?!?
  18. Ford-Man
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    Mishawaka, IN

    Ford-Man Member

    Be careful if you loop the one small wire over to the positive side...that wire is for the idiot light. If you go to any Advance Auto or Auto Zone...whatever McParts store you desire...they can show you the diagram out of the box. Pretty much all 3 wire alternators come with a wiring diagram to explain where the #1 and #2 wires go. On mine, one of em says to run to ignition switch, the other is to run in a loop to the idiot light...at least thats what the destructions told me.
  19. Aquaroscoe
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    Pleasanton, Ca

    Aquaroscoe Member

    I wired mine last weekend as Enjenjo described. All wires go back to the fuse panel area. I added the lamp and diode (1n5408) if I recall correctly to a switched source.
    So to recap, big wire to junction block, #1 white wire to a diode (line [cathode] closest to alt) then a lamp then to a switched 12 vdc, and finally the #2 red wire to the fuseblock non-switched point.
  20. Model A Vette
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    Central NJ, USA

    Model A Vette Member

    Maybe this will help?

    Attached Files:

  21. Deville1904
    Joined:
    Dec 31, 2007
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    Sur Califas

    Deville1904 Member

    Well now I just have to find the right alternator locally. Im looking for the 12si type by delco remy. I think its model number 7127. Anyone know if I can get this at autozone, pepboys, kragen? Anyone in san diego want to come over and help me wire it so I dont burn the cadillac down? Ha ha ^_^
  22. Model A Vette
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    Central NJ, USA

    Model A Vette Member

    Yes, Autozone should have one.

    The answer to their question is: "75 Chevy Nova with A/C."
  23. Classic Boatworks
    Joined:
    Jun 23, 2010
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    Location:
    California

    Classic Boatworks Member

    Good info. I have a situation where at idle the alternator is putting out 13+ volts. When in gear and running drops as low as 8 volts. Scratch your head on that one! Had both alternator and battery checked. The wires from the alternator run to the starter. I have headers and getting to the starter is a real pain. My plan is to rewire #1 and #2. #1 I can pick up power at the positive side of the coil (right?). You mention #2 at the fuse box. Where on the fuse box will I attach the wire? 1985 GMC 350.
    Thanks,
    Dean

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