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3G Alternator Conversion


This conversion was done to my 1989 Mercury Grand Marquis. It applies directly to 87-91 2G internally regulated Mercury Grand Marquis and Ford Crown Victoria's.
I will also cover swapping the 3G in place of the older externally regulated alternators--Take note however that the earlier swap is pure theory and conjecture based on deep study of wiring diagrams and pieced together information found scattered across the web.

As always, it is up to you, the end user to verify any information you get from these pages, and take full responsibility for your own work. This information is presented based on information I gathered and may not be complete or correct.

As always, double check all electrical work before applying power! This is not an option.

Reasons abound to do this swap, but my primary choice for the 3G was it was all that I had available to me at the time. Trail engineering right at home. The other primary benifit is that the 3G has a much improoved low rpm output. On the CV/GM with an OEM 65A 2G alternator headlights tend to dim when you come to a stop sign. Voltage drops if you even look at the 'on' switch for any accessory.
Also, the fact that the 2g uses an insanely stupid design for its output leads (two female spade lugs) that tend to degrade over time (in extreme cases causing fires) makes this swap a simple choice.

Pertinent alternator trivia

Parts You Will Need

3G Terminals


(alternator image taken from web, unknown origins. Text added by me.)

On to the swap...

...as it was done with my '89. The alternator used was from a 1993 3.8L Taurus, 130amp 3G. I also required the alternator bracket from a 100amp externally regulated cv/gm (find one with a heated windshield) to fit the larger 3G into my car. Both alternator and bracket came from an auto wrecking yard.

-Disconnect your battery negative cable.

-unplug everything from your old alternator

-remove old alternator.

-remove the bracket and "tripod", neither will be reused.

-install bracket obtained from a 100amp externally regulated 5.0L cv/gm (these are found on cars with the heated windshield (gold colored windscreen) or on police issue 5.0L cars).
It is also possible that the bracket from the 351cid equipped cv/gm will work. Try it at your own risk, this is unverified but provides a potential source for brackets if you want the larger 3G.

-install the original pulley onto the 3G.
The taurus pulley has a larger diameter than the stock pulley and if used will require you to find a larger belt to fit. I suggest using your original pulley, the smaller size of the original will also be benificial to low rpm output along with allowing you to use the stock specified belts. One less thing you need to remember when going to the parts store for replacements.

-install 3G using proper metric adjuster bolt

-plug regulator plug into regulator

-cut the output wires and stator wire out of the 2G plug.

  • stator wire is 18 guage white/black
  • output wires are 10 guage red/black wires
  • connect the stator wire to the one wire stator pigtail and plug into the stator plug
  • attach the two output wires together with a ring terminal that fits onto the output stud, slip onto stud.

    -connect a brand new 4 or 6 guage wire (with ring terminal) to the output stud and run it to the starter solenoid area--attach to a 125amp (or larger, upto 200amp) fuse. Connect another short length of the same size wire to the hot side of your starter solenoid. Thats the side thats connected to your battery.

    Many people ask this question, "Why put in a fuse?", I'll tell you why, if you don't and your alternator shorts you WILL have an engine compartment fire. When the alternator shorts, it will drain the battery through the output wires and the power required of a battery to start a car is more than enough to start a fire when it is left unchecked.
    THE FUSE IS _NOT_ OPTIONAL You must install one.

    Double check all your wiring, make sure your belt is adjusted, and fire up the car. Measure the voltage at the battery and you should see 14.x volts with only minor drops when turning on accessories.




    Swapping out Externally Regulated Alternators

    Almost as easy as swapping out the 2G.
    Coming soon.

    Final Thoughts

    If using a small frame 3G you may or may not need to discard the "tripod" bracket. It makes little difference as the stock 100amp units do not use a tripod bracket anyhow.

    If your car is equpped with the heated windshield this swap will NOT work due to how the heated windshield system operates. You can disable the heated windshield option (email me for details) and will be able to proceed.

    Use proper terminals and crimp and shrink wrap as necessary

    Document any changes you make to circuits.

    Do not use your electrical wiring to hang things.
    Leave sufficient slack in your wiring so flexing or contraction stresses do not compromise wire crimps or connections.

    Double check everything and dress wires appropriately.


    This information is only intended as an overview and may not include all the necessary information, data, or facts.
    Every vehicle is unique, and research for your particular vehicle is recomended.


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    This Page Created By Alexander M. Bilan (gmguy89@netscape.net)
    All Rights Reserved.
    December 25, 2003
    Revision 1.1 January 3, 2003