How does the Ford 3G alternator connect to the battery?

Per the diagram, the alternator B+ output runs through a MEGA FUSE on a red wire directly to the battery positive terminal.

What wire colors are used on the 3G alternator regulator plug?

The diagram shows W/BK (White/Black) on the stator S terminal, Y/W (Yellow/White) on the A terminal, and LG/R (Light Green/Red) on the I terminal to the charge lamp circuit.

What resistor is used with the instrument cluster charge lamp?

A 510-ohm resistor is shown in parallel with the optional instrument cluster charge lamp on the LG/R circuit.

What fuse feeds the charge indicator circuit?

A 20A fuse in a 'Hot in Run' circuit feeds the LG/R wire that goes to the charge lamp and the regulator I terminal.

What are the internal components shown inside the 3G alternator?

The diagram shows the stator, rectifier (diode bridge), B+ output, and the regulator containing sensing and switching circuits plus the field winding.

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Ford 3G Alternator Wiring Diagram - Mega Fuse, Charge Lamp & Wire Colors

Ford 3G alternator charging circuit wiring diagram with mega fuse, battery, regulator, and color-coded wires

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Wiring diagram of the Ford 3G alternator charging circuit showing mega fuse, battery, regulator sensing/switching, and Y/W and LG/R wires.

AI caption October 2020 · Photo 4 of 17

This document is a color-coded wiring diagram for a Ford 3G alternator charging system. It shows the alternator's internal components — the stator, rectifier (diode bridge), and voltage regulator with its 'sensing and switching circuits' and field winding — and how the unit connects to the vehicle's electrical system. The alternator B+ output feeds through a MEGA FUSE (no amp rating shown) via a red wire to the battery positive terminal. Three regulator-side connections are labeled: the S (stator) terminal uses a White/Black (W/BK) wire, the A (sense) terminal uses a Yellow/White (Y/W) wire routed to the battery-side circuit, and the I (indicator) terminal uses a Light Green/Red (LG/R) wire that runs to an optional instrument cluster charge lamp (with a 510-ohm resistor in parallel) fed by a 20A 'Hot in Run' fuse. A reader can learn the correct wire colors, terminal identifications (B+, A, S, I), fusing arrangement, and the charge-lamp/resistor circuit needed when installing or troubleshooting a 3G alternator, such as during the popular 3G alternator upgrade on older Ford trucks. The diagram carries a 2005 copyright watermark but does not state a specific model year, model, or engine applicability.

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Frequently asked questions

How does the Ford 3G alternator connect to the battery?: Per the diagram, the alternator B+ output runs through a MEGA FUSE on a red wire directly to the battery positive terminal.
What wire colors are used on the 3G alternator regulator plug?: The diagram shows W/BK (White/Black) on the stator S terminal, Y/W (Yellow/White) on the A terminal, and LG/R (Light Green/Red) on the I terminal to the charge lamp circuit.
What resistor is used with the instrument cluster charge lamp?: A 510-ohm resistor is shown in parallel with the optional instrument cluster charge lamp on the LG/R circuit.
What fuse feeds the charge indicator circuit?: A 20A fuse in a 'Hot in Run' circuit feeds the LG/R wire that goes to the charge lamp and the regulator I terminal.
What are the internal components shown inside the 3G alternator?: The diagram shows the stator, rectifier (diode bridge), B+ output, and the regulator containing sensing and switching circuits plus the field winding.