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Mopar alternator questions (or people with electrical smarts)

Discussion in 'The Hokey Ass Message Board' started by NAES, Mar 2, 2012.

  1. NAES
    Joined: Dec 24, 2008
    Posts: 434


    Hey all, I killed the alternator in my wagon and have been having a hard time getting the correct one from my local parts house. I have a 3 wire set up that is from the 1970 and up era similar to the one posted on the right. The alternator that went out has the power wire and 2 field plugs. One positive and one negative which get plugged into an external regulator. See attached diagram.



    The unit that shows up in the parts house catalog looks completely different with a single field pole and a ground lead instead of an additional field wire.

    The parts house guy says I can run both leads to the same field pole but that makes no sense to me since they are going to 2 completely different parts of the regulator. In my thinking it tells me that I will be charging at full blast the whole time probably frying the regulator in no time flat.

    Please let me know what I need to get to finish the job right and get back to driving.

    Thanks all, NAES
  2. llonning
    Joined: Nov 17, 2007
    Posts: 677


    The dating is wrong on that. Pre 1970 was a single field wire. I can't remember if it was '72 or '73 they came out with the dual field wires. I used to know how to re-wire the 2 field set-up, but it has been a long time since I had to do that.
  3. brad2v
    Joined: Jun 29, 2009
    Posts: 1,617


    1) Kick the parts house guy in the nuts
    2) Go to a different parts house
    3) Just tell 'em it's a '73 Dodge Dart 4 door, 318, green, no a/c, 3 hubcaps, and all the other nonsense you have to answer to get parts anymore
    BTW, I'm not bashin' parts guys, I are one. But there aren't many left that can read. Or think.
  4. AL_JACK
    Joined: Feb 18, 2008
    Posts: 10


    An alternator with an external (or internal) regulator controls the amount of current in the field winding based on the battery voltage. As the battery voltage increases to its fully charged value, due to the alternator charging the battery, (around 14v ) the field winding current is reduced by the regulator. At full charge (voltage) the field current is reduced to almost zero. Typically, a transistor in the regulator, switches on and off to control the field current. The lower the battery voltage, the longer the transistor switch is on to give a higher average current into the field, increasing the charging current from the alternator. Hope this helps.

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  5. Von Richthofen
    Joined: Oct 28, 2009
    Posts: 246

    Von Richthofen

    Here is my set up from a Dyplomat. The green wire
    off the regulater goes to green wire on alt, I forgot
    to put one on and burned up a new battery :rolleyes:

    Attached Files:

  6. Big_John
    Joined: Mar 28, 2006
    Posts: 327

    from Upstate NY

    You can use a dual field alternator in an single field (pre 1970) car by using a jumper on one field to ground, but you can't use a single field alternator on a dual field (1970 and up) car.

    The parts guy is a dumb ass.
  7. 50dodge4x4
    Joined: Aug 7, 2004
    Posts: 3,536


    The wiring diagram you posted is for the 69 and older charging system.

    The 70 and newer (with the electronic voltage regulator) and the 2 field wires have one field wire connected to the ignition system (before the resistor). The second field wire connects to the side terminal on the regulator, the centered terminal on the voltage regulator connects to the ignition system ballast resistor (switch side). For the electronic regulator to function correctly, the regulator body has to have a good negative ground.

    My poor old book is in bad shape from years of use or I would try to scan the picture. Gene
  8. Moneymaker
    Joined: Sep 19, 2011
    Posts: 320


    Double field Mopar alternators were introduced in 1970.
    If you install a single field unit, it will work but charge full blast all the time and over cook your battery.
  9. Dane
    Joined: May 6, 2010
    Posts: 1,353

    from Soquel, CA

  10. NAES
    Joined: Dec 24, 2008
    Posts: 434


    Back to the parts house for the correct alternator and new voltage regulator. All is good now.

    THanks so much guys. NAES

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