How to Select and Install a High-Performance Alternator in a Subaru Legacy GT for Audio Upgrades?

The heart of your Subaru Legacy GT’s electrical system is the alternator. It feeds power to the car’s electrical components and charges the battery. If you’re looking to upgrade your car’s audio system to include high-powered amps and speakers, you might find your stock alternator isn’t capable of handling the increased load, causing your lights to dim and your engine to strain.

To avoid these issues, you’ll need a high-performance alternator. This article will guide you through selecting the right type and size of alternator, and how to install it in your Subaru Legacy GT.

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Selecting the Right High-Performance Alternator

You must be careful when selecting a high-performance alternator for your car. The alternator should be capable of handling the electrical load of your upgraded audio system, and it should fit in your car’s engine bay.

The first thing you need to consider is the alternator’s power output. A typical car audio system requires around 100 amps of power. If you add high-powered amps, subwoofers, or other audio components, you might need an alternator capable of delivering 200 amps or more.

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Another critical factor to consider is the alternator’s physical size. You need to ensure that the alternator will fit within the engine bay of your Subaru Legacy GT. Measure the diameter and length of your current alternator and compare it to the dimensions of the high-performance alternator.

Lastly, check the type of alternator. Some brands, like Fosgate, make high-performance alternators specifically designed for car audio upgrades. These alternators often have a higher voltage output, perfect for powering high-performance amps.

Installing the High-Performance Alternator

Once you’ve selected your high-performance alternator, the next step is installation. This is a task that requires some technical skills, but with the right tools and instructions, you can do it yourself.

First, disconnect your battery to avoid any electrical mishaps. Next, locate your car’s current alternator. It’s typically on the front of the engine and is connected to the battery with a thick wire.

Next, loosen the tensioner pulley to remove the serpentine belt from the alternator pulley. Now you can disconnect the battery wire and the plug from the back of the alternator. Remove the bolts holding the alternator in place, then remove the alternator.

Installing the new alternator is basically the reverse of the removal process. Bolt the new alternator in place, connect the plug and the battery wire, then reinstall the serpentine belt.

A Note on Wiring

When upgrading your alternator, it’s important to also upgrade your charging wire. A standard wire may not be capable of handling the increased power output of a high-performance alternator, which could lead to overheating and damage.

The wire size you need will depend on the alternator’s power output and the wire’s length. For a 200-amp alternator, a 4-gauge wire is typically sufficient. However, if the wire is longer than 10 feet, you may need to upgrade to a 2-gauge wire.

To install the new wire, first disconnect the old wire from the battery and the alternator. Then, connect the new wire to the alternator and battery, ensuring a secure and tight connection.

On-going Maintenance

Installing a high-performance alternator and appropriate wiring is only part of the process. It’s also crucial to keep an eye on your alternator and electrical system’s health.

Regularly check your alternator’s voltage output. A healthy alternator should output between 13.5 and 14.5 volts when the engine is running. If the voltage is too high or too low, it could indicate a problem with the alternator.

Also, listen for any unusual noises. A failing alternator often makes a whining or grinding noise. If you notice any such sounds, it’s time to get your alternator checked.

In conclusion, upgrading your car’s alternator is a necessity when installing a powerful audio system. By carefully selecting the right alternator, installing it correctly, and monitoring its performance, you can enjoy your high-powered audio system without stressing your Subaru Legacy GT’s electrical system.

Selecting the Right High-Performance Alternator: A Deep Dive

Choosing the ideal high-performance alternator for your Subaru Legacy GT entails more than just picking one that offers huge power output. You also must ensure the chosen hardware fits snugly in your car’s engine bay and is compatible with your car’s electrical system.

When considering power output, remember that an average car audio system demands around 100 amps. Adding high-powered components like amplifiers, subwoofers, or the latest head units could push this requirement to 200 amps or even higher. Brands like Rockford Fosgate are renowned for manufacturing high-performance alternators designed specifically for audio system upgrades. Their products often offer higher voltage outputs, perfect for turbocharging your audio systems.

Size is just as important as power. The alternator must fit into your Subaru Legacy’s engine bay without any issues. Before making a purchase, measure your currently installed alternator’s diameter and length, then compare these dimensions with those of prospective alternators.

Also, be sure to check the alternator’s type. For instance, a performance car alternator from Rockford Fosgate is designed with high-powered audio systems in mind. It’s crucial to select an alternator that matches your specific needs to avoid overloading your electrical system or other unwanted effects.

Installing the High-Performance Alternator: Step-by-Step Guide

Once you’ve picked the perfect high-performance alternator, it’s time to install it. While this task requires a level of technical proficiency, with the right tools and guidelines, you’d be surprised how easy it can be.

Start by disconnecting your battery. This eliminates the risk of electrical accidents during installation. The alternator is typically positioned at the engine’s front and linked to the battery with a thick wire.

Next, you’ll need to loosen the tensioner pulley to free the serpentine belt from the alternator pulley. Once this is done, disconnect the battery wire and the plug from the alternator’s back. You can then proceed to remove the bolts holding the alternator and carefully remove the alternator itself.

Installation of the new alternator is essentially the reverse of the removal procedure. Secure the new alternator with the bolts, connect the plug and the battery wire, and finally, reinstall the serpentine belt.


In the final analysis, upgrading your Subaru Legacy GT’s alternator is an essential step towards enjoying a powerful audio system. It’s not just about selecting the right alternator; the installation process, coupled with the need for an upgraded charging wire and ongoing maintenance, is equally important.

By taking these factors into account, you can experience your tunes in high performance without overloading your electrical system. So, whether you’re a team owner preparing your car for a show or a music lover looking to enjoy good quality sound on the go, following these steps will make sure your Subaru Legacy GT offers a fantastic front stage for your audio entertainment.

Remember, it’s not just about opening the window and letting the world hear your sound; it’s about doing it in a way that’s safe and sustainable for your car. Happy listening!