What Is An Alternator And Why Is It Important?

You know how some car parts are so important that your car can't function at all without them? The alternator is one of those parts. Your car relies on the alternator to power the entire car while it's running, and charge the battery at the same time.

If you're looking to learn more about alternators, this is the guide for you.

What Is An Alternator?

Oem alternator drawing

Toyota alternator #27060-74750-84: for 1998-2000 RAV4s

Attached to the engine via a pulley is an alternator. The alternator is a small generator that creates electricity for all the things in your car that need it, such as:

  • The dome lights
  • The dash panel
  • Heat/AC fan
  • Stereo
  • Power mirrors and seats
  • Brake lights
  • Headlights
  • Turn signal lights

You may be thinking, "hey, doesn't the battery power these things?" If you are, then you're correct. The thing is, the alternator charges the battery. Its sole purpose is to produce electricity for the battery, so that it does not become run down while the car is in use.

What Does An Alternator Look Like?

OEM toyota alternator

A Toyota alternator is a pretty small device. It's the size of a grapefruit, and it's about 6 pounds, give or take. Here's what a Toyota alternator looks like:

The alternator design varies between Toyota models. Yet, all alternators have two things in common:

  1. A bunch of ventilation holes to help keep them cool.
  2. A rotor inside. That rotor spins and generates energy to charge the battery.

An alternator has four major components:

  1. Stator
  2. Rotor
  3. Diode
  4. Voltage regulator

How Does An Alternator Work?

The alternator starts powering the battery as soon as you turn on the engine. Here's how the process works:

  1. The ignition switch is turned on.
  2. The engine starts running.
  3. The drive belt begins turning the alternator pulley.
  4. The rotor, which is attached to the alternator pulley, starts spinning. This creates electricity via electromagnetism.
  5. The electricity flows to the diode via the stator, and the diode converts the electric current from AC to DC.
  6. The DC current flows to the car battery via the voltage regulator.
  7. The battery powers the vehicle's electrical system.

Does An Alternator Ever Go Bad?

Toyota alternator placement

An alternator in action. Source: Phasmatisnox via Creative Commons 

An alternator typically lasts about 100,000 miles. Time isn't kind to alternators because many different components can eventually wear out. It's common for the following parts to wear out:

  • Alternator pulley
  • Diodes
  • Voltage regulator
  • Stator
  • Bushings
  • Coil
  • Bearings

It's also possible for an alternator to fail early. The following scenarios are not unheard of:

  • The alternator pulley breaks because it was installed too tight.
  • The alternator fails because it was not refurbished correctly.
  • A brand new alternator fails because someone dropped it before installing it. Dropping an alternator can break a cable connection and/or loosen the bearings.

How Much Does A New Alternator Cost?

A brand new OEM alternator can cost as much as $900 or as little as $150. It depends on which Toyota model you have. You can buy a remanufactured alternator at a lower cost.

To save the most money, order an OEM alternator online. Toyota dealerships impose a hefty markup on their parts. Authorized online sellers, like us, have much lower overhead costs, so we're able to offer lower prices. We actually have wholesale pricing, which is pretty hard to beat. We also sell refurbished alternators. Take a look at our catalog of genuine OEM alternators to see what we have to offer!

Written by Jason Lancaster