Which wire on the stock alternator harness needs to be modified for the 3G swap?

Only the White/Black-striped wire. The diagram warns not to mess with the other wires on the D-shaped plug.

What happens to the rectangular plug when installing the 3G alternator?

The rectangular plug is discarded. Its wires are cut at the points marked "Cut Here" in the diagram.

How does the White/Black stripe wire connect to the 3G alternator?

It gets a female spade connector that plugs into the spade terminal on the 3G alternator.

Where do the heavy charging wires attach on the 3G alternator?

They get ring connectors that are connected to the charging post (small bolt) on the alternator.

What wire colors are on the D-shaped plug?

The D-shaped plug carries a Yellow/Tan stripe wire and a Green/Red stripe wire, plus the White/Black stripe wire runs to it in the diagram.

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Ford 3G 130 Amp Alternator Upgrade Wiring Diagram - Harness Modification

3G 130 amp alternator upgrade wiring diagram with color-coded plugs and connectors

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Alternator upgrade wiring diagram showing D-shaped and rectangular plugs, color-coded wires, charging post and ring connectors.

AI caption October 2007 · Photo 41 of 78

This document is a two-panel wiring diagram illustrating how to convert a Ford stock alternator harness for use with a 3G 130-amp alternator. The left panel shows the stock alternator with its two connectors: the D-shaped plug (carrying a Yellow/Tan stripe wire and a Green/Red stripe wire) and the rectangular plug (carrying the White/Black stripe wire and heavier charging wires). A prominent warning states not to modify the other wires on the D-shaped plug—only the White/Black-striped wire should be changed. Two "Cut Here" callouts indicate where to sever the rectangular plug's wires. The right panel shows the 3G 130-amp alternator installation: the rectangular plug is discarded, the White/Black stripe wire receives a female spade connector that plugs into the alternator's spade terminal, and the heavy charging wires get ring connectors that attach to the charging post (small bolt) on the alternator. Final instructions read: connect the rings to the charging post, plug in the spade, and plug in the D-plug. A reader learns which wires to cut, which wire colors serve which function, what connectors to crimp on, and where each terminates on the 3G alternator.

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Frequently asked questions

Which wire on the stock alternator harness needs to be modified for the 3G swap?: Only the White/Black-striped wire. The diagram warns not to mess with the other wires on the D-shaped plug.
What happens to the rectangular plug when installing the 3G alternator?: The rectangular plug is discarded. Its wires are cut at the points marked "Cut Here" in the diagram.
How does the White/Black stripe wire connect to the 3G alternator?: It gets a female spade connector that plugs into the spade terminal on the 3G alternator.
Where do the heavy charging wires attach on the 3G alternator?: They get ring connectors that are connected to the charging post (small bolt) on the alternator.
What wire colors are on the D-shaped plug?: The D-shaped plug carries a Yellow/Tan stripe wire and a Green/Red stripe wire, plus the White/Black stripe wire runs to it in the diagram.