Posted on: September 26, 2016

in the June 1982 RootesReview:

A number of people have written asking for information on how to convert from a generator to an alternator. Although this is not a difficult conversion, I felt the length of the answer was more suited for a Tech Tip, rather than a Q & A piece.

Sizing the Alternator

The first step is to determine what ampere rating alternator your car needs. Add up the power needed to run all of your electrical items, then pick an alternator with excess capacity.

The 1970-74 Ford alternators were color-coded:

  • purple (38 amperes/570 watts);
  • orange (42 amps/630 watts
  • red (55 amps/825 watts);
  • green (61 amps/915 watts); and
  • black (65 amps/975 watts).

The regulators are color coded to match, the electromechanical type being more durable than the transistorized type.

Parts Needed

Once you have obtained the proper alternator, it’s time to gather the rest of your parts. You will need 8 to 11 feet of 10 or 8 gauge wire (brown insulation, if possible), a heavy duty 15-ohm resistor and brackets to mount the alternator. I am told that you can use a D4A2-10156-A bracket, a D08A2-8A652-A spacer and a D002-10145A adjustment bar.

If you use the PH 45 filter, you can mount the alternator where the stock filter goes using C92E-10A336-A bracket off of a ’69 351 Mustang with a C3AE-10145-A adjustment bar from a ’63 Galaxie.

Wiring

Now that you have all your parts together, you are ready to rewire. First, disconnect the battery. Attach the large brown/yellow wire to the alternator field and the brown/ green wire to the starter terminal. Ground the alternator with the black wire (early Tigers may not have this wire). Use the new wire to make a circuit from the battery terminal to the battery side of the starter solenoid.

Mount the regulator in place of your old one. Take the two smaller brown wires from the B terminal of the old regulator and attach them to terminal 1 on the fuse block (there should be another brown wire there). The remaining large brown wire should be connected to the A+ terminal on the new regulator. The small brown/yellow wire from terminal D gets attached to terminal I, while the larger brown/yellow wire goes to terminal F. The brown/green wire from the old regulator’s terminal F goes to the new terminal S.

Finally, take the resistor and wire it in parallel with the ignition warning light. It should be attached to the brown/yellow wire on the one side and the white wire on the other. Caution: If the resistor is not large enough it will heat up and can cause a fire. As long as all your connections are good, you should now be ready to charge.

(Ed Note: also see M27 – Tiger Alternator Conversion II)

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