A103 12 Volt, 120 Amp, GM Alternator
12 Volt, 120 Amp, GM Alternator

Chrome One Wire 12 Volt, 120 Amp, GM Racing Alternator

Easy Hookup, Compact Size & Light Weight
Part # A103
In stock - Usually ships in 1-2 Business Days
Only $189.00 ea
Features: Chrome Plated 120 Amp, 14 Volt Regulator GM Style weighs only 12 lbs. Includes 2.5" V-Belt Pulley.
Bracket Kit Options: (please read application notes below)

Alternator Bracket Kit Option

Brace Style Bracket Option

Get everything you need to mount your new GZ Motorsports Alternator with this time saving Bracket Kits. This Brace Style Alternator Bracket Kit allows a compact clean installation with the alternator mounted where you want it. Kit includes 5" dia crank pulley, Brace Bracket Mount, all studs, bolts and spacers needed (wire not included).

Application Notes: Stud bolt head /block mount works with most applications, call to verify.


Stylish performance in a small package

With the accessories many of today's race cars have such as electric fuel pumps, fans, nitrous solenoids, water pumps and hi-amp electronic ignition boxes, generating adequate current is essential for race winning performance. This GM style alternator has a 120 amp punch to keep up with your electrical accessories and it's chrome plated to look great in your engine compartment. Single wire hookup means less electrical headaches, it's simple to hookup and get running fast. Features a 6.25" mounting bolt circle and is 5.5" deep from belt centerline to rear of alternator.


  • 120 Amp Output
  • 2.5" Diameter V-Belt Pulley Included
  • For 12 Volt DC Systems
  • 14 Volt Regulator Setting
  • 6.25" Bolt Circle
  • 5.5" from Belt CL to Rear Housing
  • 12 lbs Shipping Weight
  • Requires 2500 RPM at Alternator Pulley to Activate Charging
  • 16,000 Alternator Pulley Max RPM

One Wire Racing Alternator Instructions

The beauty of the one wire alternator design is it's very simple to hook up, just run a charge wire from the positive battery terminal (or battery side of shutoff switch) to the stud terminal on the alternator. This design uses a self exciting field which means when it spins at a sufficient RPM, the alternator will start charging. When the engine stops rotating, it turns itself off.

Keep in mind that the engine has to be turning around 1300 RPM in order to spin the alternator at 2600 RPM in order to get it to start charging. Just start the engine and "blip" the throttle in order to get the alternator to turn on. You don't have to keep the RPM up, once the alternator is energized with a quick blip you can let the engine idle back down.

The maximum RPM on this alternator's shaft is 16,000 RPM, which means if you have a 2-1 pulley ratio, the highest RPM you should turn the engine is 8000 RPM. If the max rpm is exceeded it can cause damage to the internal armature and cause a failure. Please keep this in mind when choosing your crank pulley size. Note that most street pulleys are 3-1 ratio, which for a typical racing engine can spin a alternator too fast.

Do not over tighten the belt! Install the belt and adjust so that there is approximately 1" free play in the belt when measured half way between the pulleys. Don't forget to tighten all bolts.

This One Wire Alternator Wiring Diagram [PDF Format] may be helpful if you're wiring a car up from scratch.

Charge Wire Size

This alternator can output a maxiumum of 120 amps at 14 volts, for the best performance and reasonable amount of voltage drop, you should use a 6 AWG cable for a 5 ft or shorter charge wire. For rear mounted batterys with charge wire lengths between 6 to 15 ft use at least a 4 AWG or larger cable.

Emergency Shutoff

If you run the charge wire from the alternator to the starter, or other location instead of running direct to the battery, you must add a continous duty relay in line with the charge wire to prevent the engine from continuing to run when the emergency disconnect is thrown. We recommend using a Ford Style Continuous Duty Relay for this purpose.