What Does An Alternator Do?

What exactly is an alternator and what does it do in a car? How do you tell if your alternator is working properly? Here is a simple guide.

By the look, many people confuse the alternator for a turbocharger, while others confuse its function with the car battery. In this article, you will learn how an alternator works and what it does.

The alternator is usually located on the front side of the engine. The function of the alternator is to produce electricity to power your car accessories, such as the air condition, headlights, electric windows, and so on.

You might be wondering: How exactly does this process work? In the following text, the whole process will be described comprehensibly.

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The Components Of An Alternator

alternator repair cost

Before the procedure is described in detail, the fundamentals of the alternator have to be assessed in order to fully comprehend the process.

The alternator is made up of multiple components that work together to produce electricity. Two components that stand out and are the “bread and butter” are the so-called rotor and stator.

 Other important components include:

  • Pulley
  • Voltage regulator
  • Rectifier

Even though the stator and rotor are the heart of the alternator, it would not be possible for your engine to receive power without all the components working together.

Other components such as the housing and bearing will also be shortly written about.


As the engine starts producing power, the up-and-down movement of the pistons gets converted to a rotational movement at the crankshaft.

Attached to the rotating crankshaft is a serpentine belt attached to a pulley. The same belt is connected to the alternator pulley.

The alternator pulley rotates the whole assembly, or more specifically, the rotor.

If this sounds foreign to you, or you would like to freshen up your memory, make sure to read our comprehensive guide “How Does A Car Engine Work”. The process is described in a simple and easy-to-understand manner.


car alternator rotor

An alternator work by electromagnetic induction. In other words, it works by producing electricity by a spinning magnet (the rotor) and a loop conductor (stator).

Unless you have recently studied physics or work with electricity, these terms might be a little confusing.

Put it simply, electricity is the flow of electric charge. All substances consist of atoms, which in turn, consist of electrons, protons, and neutrons.

As the electron’s spin around the atom’s core, an electric current is produced. Depending on the direction of the electrons, a substance will be either weakly magnetic or strongly magnetic.

A magnet will have a north pole and a south pole, where the opposite pole attracts each other. The rotor, in this case, will rotate inside the stator, pushing the electrons in it.

As previously noted, electricity is the flow of electric charge. As the rotor pushes the electrons into the stator, a literal flow of electrical charge occurs.

In case you would like to learn more, Wikipedia has a great and detailed article explaining the phenomenon.

The rotor consists of “claw poles”. One side of the “claw” consists of a north pole, while the other is a south pole. Being close to each other, and alternating from north to south, a big magnetic field forms.

In other words, the rotor works as an electromagnet. By the rotational movement of the pulley, it will spin and act as a magnet, pushing electrons to the stator.


By now, you might have noticed that the stator plays a big role together with the rotor.

The stator is what surrounds the rotor. It is stationary and consists of coiled copper wire. As the rotor spins, electrons will be pushed to the stator.

To put it simply it is a receiver of electrical current that later. Because of the spinning motion of the rotor and the different magnetic poles, alternating current is produced.

Voltage Regulator

car voltage regulator

The voltage regulator determines the amount of power that is distributed from the alternator. It is important how much the output of the alternator is.

If the voltage is too high, it can damage electrical components of the car such as the battery. A low voltage drains your battery, and the electrical components will not work properly.

The voltage regulator compares the power taken from the stator to the voltage of the battery. If the battery voltage is lower, the voltage regulator will increase the voltage from the alternator.

By powering the wires in between the claw poles, a greater electromagnetic effect will occur, producing more power. It does so with the help of brushes that are located at the rear of the alternator.

Remember that the rotor is powered by the pulley which speed depends on the engine speed. By having a voltage regulator, the voltage can be regulated regardless of engine speed (as long it is not zero).


The alternator gets its name from the current it produces – alternating current. It is called alternating as the polarity changes as the rotor spins.

In order for the battery and other electrical components to work, direct current (DC) has to be used instead of alternating current (AC).

A rectifier converts the alternating current produced by the rotor and stator, to direct current. The direct current is then used to charge the battery and power electrical accessories of the car.

The Function Of An Alternator

Car Alternator

As stated above, the way an alternator work seems simple, yet there are a lot of things that makes an alternator produce electricity.

The battery is responsible for starting the car and storing electricity when the engine is not working. As you turn on the engine, the alternator replenishes the battery and hinders it from depleting.

The alternator powers almost all electrical components that you use in your car such as the AC, power windows, heated seats. and so on.

Because of that, a problem with, for example, your power windows may be due to an issue with an alternator. If you suspect a faulty alternator, you can test it easily with a voltmeter.

Luckily, it is not very common for an alternator to go bad, but it does happen. If you are one of the unlucky ones, you would either have to repair or replace it, which can cost from $100 up to $1000.

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Bajro Muric
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Bajro is a big car enthusiast with a love for writing and teaching. He writes about anything regarding cars - from common problems and fixes to racing.