What an Alternator Does and When to Replace Yours

What is an Alternator?

Your car’s battery gets a lot of attention; it’s tested during most maintenance appointments, and blamed during many breakdowns. But behind the battery (not literally) lies an unsung hero; the alternator. Alternators in essence create AC power to recharge the battery through a connection with the engine. Without an alternator a car battery won’t last long at all and the car will be essentially inoperable. The engine won’t start without electricity to drive the starter motor, and even if it could start, it would not run without electricity to operate the spark plugs.  Think of an alternator as a generator for the electrical components of you vehicle as well as a charger for your car battery.

How Do Alternators Work?

Most alternators are coconut sized devices driven by a serpentine belt attached to the crank shaft. Inside the alternator, a rotor spins inside of a surrounding “stator.” Both the rotor and stator make up their own electromagnetic fields; when the rotor field spins inside of the stator field AC power is generated inside of the stator. At least, that is the generalized explanation. For a more in depth explanation of how alternators work, check out this How Stuff Works article.

Why Do Alternators Fail?

Like any mechanical component, alternators are prone to fail after long time use. Because they are placed so close to the engine, alternators live in a harsh and hot environment. Additionally, the rotor inside an alternator spins extremely quickly and extremely frequently. After billions of revolutions, it is no surprise that rotor bearings may go bad in addition to other alternator parts. If your car has a worn battery, the alternator may have to work especially hard to keep it charged. This may decrease the life of an alternator. Aftermarket accessories such as high powered subwoofers or lights may also cause excessive battery drain and premature alternator failure.

When Do Alternators Fail?

Alternators have no set life span, but they usually give off warning signs before failing completely. These include;

• A warning light on most new vehicles
• Erratic radio, light, or other electrical component functioning
• Strange grinding, growling, or whining noises
• Burning rubber or hot metallic scents
• A battery that frequently dies, or that stays dead

If your vehicle displays any of these symptoms bring it in for a checkup as soon as possible or risk being left stranded.

Replacing an Alternator

Replacing an alternator is a job that some weekend mechanics may be able to take on, but in most cases it’s a more complicated process than just bolting a new alternator on. Alternators are often hidden deep inside the engine compartment and other engine components need to be removed to access the alternator. Check the Fisher Service Specials Page for discounts and make an appointment to let Fisher Service take care of your alternator.