Rob Kinnan
Brand Manager, Mustang Monthly
February 1, 1999
Photos By: Brendan Maze

Step By Step

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The stock Mustang 5.0 alternator (right) puts out a max of 75 amps, compared to the later-model (‘94 and up) 130-amp unit (left).
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GRC’s conversion kit comes with the alternator, a short piece of wire with the appropriate connector, a ring terminal, and a boot.
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The 130-amp alternator is physically larger than the stocker, so the bracket must be trimmed a little bit with a cutoff wheel.
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The pivot end of the alternator needs just a hair of a trim to fit the bracket. Only about .010-inch needs to be removed, so you could quickly do it with a file if that’s all you have.
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The adjuster bolt hole must be tapped for 12mm x 1.75 threads.
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To remove the pulley from the stock alternator and install it on the new one, an impact wrench is the hot ticket. Otherwise, it’s nearly impossible to keep the alternator from turning.
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The stock alternator has two connections on the back, but the 130-amp has three. There are two three-wire plugs in the harness, a big one and a small one.
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The small one plugs into the 130-amp alternator without modification, but the big plug needs to be cut off and new wires spliced in to mate up with the new alternator.
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This schematic shows how to wire it up, using the supplied wire and ring terminal. The rubber boot is used with the ring terminal to prevent a short.
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Finito! Now you can add that tri-amped stereo without fear of losing power.

The stereo hounds know that a Mustang's factory alternator is completely inadequate when the boom level gets increased with multiple amplifiers and all the other forms of electronics we stuff into our cars today. A stock alternator works just fine on a stock Mustang, but how many of us have stock Mustangs? Add in a killer stereo, a cell phone, a GPS system, or even some high-powered driving lights, crank on the air conditioning and headlights, and you'll definitely notice the voltage gauge dipping below the middle mark. Eventually, that'll kill the battery.

The fix is to install a later-model 130-amp alternator, which cranks out enough juice to keep up with most of the demands we place on it. The installation of a 130-amper is easy with GRC Performance's conversion kit. For $275, you get a brand-new (not rebuilt) alternator, instructions, and the wiring necessary to do the swap. Only minor trimming of the bracket and a bit of wire splicing keeps this from being a brutally simple remove and replace affair.