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What Is an Alternator? A Practical Guide

What is an alternator? Simply put, it’s a part of your car’s electrical system that you never really have to think about until it starts to cause you grief. Alongside your vehicle’s battery, the alternator is the backbone of the charging system in your automobile, and as such, it’s useful to understand how it works and the job it does for you during your daily commute.

What Is an Alternator Made of?

Your car needs electrical current to stay running, which means relying on more than just the battery. While the 12-volt battery under your hood is responsible for providing the juice needed to turn the starter, once the engine is running, it’s the alternator that takes over.

Inside this small device is a rotor that spins at a high rate of speed thanks to a belt that’s connected to the car’s crankshaft. The rotor spins past stator windings inside the alternator to create an electromagnetic field, which is converted by a set of diodes into direct electrical current. Alternators make use of vented aluminum housings that help to dissipate the heat generated by its operation.

The 12-volt electric current produced by the alternator is used to keep the battery charged and to power all of a vehicle’s electric systems. This includes climate control, the radio, lights and the computerized brain that manages your engine.
Warning light

Alternator Problems

As you can see, the alternator is a critical piece of equipment. But how do you determine when it’s starting to wear out? Typical symptoms include flickering or fading interior and exterior lights, warning lights on the dash going on and off seemingly for no reason and a battery that won’t charge while the engine is idling. You could also have occasional stalling or a no-start condition. At its most extreme, a dying alternator won’t provide enough energy to keep your car running properly, so once your battery drains completely, your vehicle won’t be going anywhere.

Fortunately, alternators are not an expensive component to replace, and because they are almost always located at the front of the engine itself, the replacement job itself isn’t difficult. In some cases it’s even possible to buy an alternator rebuild kit that will allow you to replace the worn out interior components while keeping the shell and much of the mechanism intact.

Check out all the electrical system products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on replacing your alternator, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Freeimages

about author

Benjamin Hunting

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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