The output of an alternator is usually expressed in amps, which is essentially the amount of current the unit can supply to all of the equipment connected to the electrical system. This is an important number because OEM alternators are typically not equipped to handle the additional loads of aftermarket equipment and upgrades.

When this happens and your alternator output can’t fully meet the needs of your electrical system, you can experience everything from dim headlights to serious drivability issues. If you don’t fix this problem, the alternator will eventually burn out completely.

Of course, there is a difference between the amperage rating of an alternator and the amount of current it can deliver at idle speed. Therefore, it is important to understand how to read alternator output ratings if you have installed a lot of aftermarket equipment that draws a lot of current.

While the output of an alternator will give you an idea of what it should produce, the only way to see what an alternator can actually do is to test it. To do this, you can measure the actual output of an alternator under a simulated load, giving you an idea of what it is capable of producing under real-world conditions.