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Ford Alternator Buying Guide

9/13/2016
Tags: Tech, Ford

When you start to look for an alternator, be it a simple aftermarket replacement, or a heavy duty performance unit, start your search at Speedway Motors. We offer three main types of alternators for your Ford: The 1-wire, which is great choice for a clean setup and easy installation, the 3-wire OEM-style replacement, or the earlier externally regulated alternator.

1-Wire

The 1-wire alternator offers a simplified installation and clean setup. It has one wire that connects the charge terminal directly to the battery or a 12V source. These will be internally regulated and ground through the block. 1-wire alternators will not have a way to hook up a warning light, but most custom applications work well with a voltage gauge in its place. The cut in speed (the speed at which the regulator begins to charge) will be slightly higher (1200rpm or higher) than most alternators which means they do not charge at idle.

3-Wire

A 3-wire or “OEM-style” alternator will also be internally regulated and have a charge post and two terminals on the side (viewed from back). Typically one terminal is for the field or exciter circuit and the rother terminal is used for the sensing circuit. They are slightly more complicated to wire up, but have the advantage of charging at lower rpm and the ability to use an original warning light.

Externally Regulated

These older style alternators can be referred to as a 2-wire, 3-wire, or even 4-wire. Regardless of the name, the important difference is that they are designed to work with an external regulator. They were used after generators were phased out from the mid 60’s until around 1985, when Ford introduced an internally regulated unit. Original Autolite models (1964-'71) had rounded corners on the cases, and when Ford switched to Motorcraft in about 1972, they also devised a convenient Y-shaped plug with caps for the connections. The newer Tuff Stuff unit shown is rated at 70 amps, compared to the 38-55 amps of original units.

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