What is an Alternator and Why is it Important?

Daniel McDonald
Daniel McDonald10 min read
What is an Alternator and Why is it Important?

Drivers need to conduct scheduled maintenance from time to time. It will keep their vehicle's electrical system in proper condition and resolve any unforeseen problems. Most importantly, one area where you should pay special attention is under the hood. This area has the most integral car parts.

Often, people believe that the battery is the primary source of electricity. That is not the case since the battery only stores the electric current. It is the alternator that generates and delivers a constant flow of electricity to the engine. They turn mechanical energy into electrical current for the batteries to charge.

The alternator is a vital part of your car's charging system. It ensures you can have a smooth journey ahead. So, it is imperative to have complete knowledge about it. If you can understand the functions of the alternator, it will enable you to spot issues with it beforehand.

We will discuss the nitty-gritty of an alternator to give you a better idea. So, without further ado, let's get right into it.

What is an Alternator?

The alternator is a vital part of your car, and it acts as a generator. It is responsible for providing electricity to the car's electrical components. Apart from some modern vehicles, you will find an alternator with a standard internal combustion engine.

There is an alternator belt to hold it with the engine. It is mounted at the front of the engine and is around the size of a coconut. The alternator has a crucial role in ensuring your car's battery and other electrical components operate properly.

Components of Alternator

An alternator comprises various components that allow it to provide the right amount of power to the different parts of your vehicle. It handles and sends power to the car's electronics, such as the air conditioner, interior lights, etc.

While your vehicle's charging system consists of multiple elements, below are the critical ones with their functions.

The components of an alternator have functions that provide the right type and right amount of power to the vehicle. Your car’s charging system contains many parts, but these are the main elements of the alternator and their functions:

Cooling fan

First and foremost, cooling fans are the most integral part of the alternators. Since the alternators realize too much heat, they need something to cool down quickly. And that is where the cooling fans come into play.

Though the vents and aluminum casing help realize heat, the fans keep the alternators cool by giving them additional cooling. While an old alternator had external fan blades, the new ones have cooling fans internally.

Voltage regulator

The voltage regulator is also an integral part of the car's electrical system. It keeps a check on the electrical energy that the alternator generates.

In addition, the voltage regulator checks the voltage level that goes to the battery and delivers the energy to the other parts of the car.

Rotor and stator

The most vital component of the alternator is the rotor and stator. These parts are essential for creating a current that runs the entire car.

A rotor is a cylindrical part, and it has magnets around it. It revolves inside the stator that has conductive copper windings. The rotor spins and the magnet's movement over the wiring generates electricity.

Diode Rectifier

Lastly, the diode rectifier helps transform the voltage coming from the alternator. It turns it into a special form for the battery's usage for recharging.

Slip Rings And Bearings

The slip rings have a critical role in getting the direct current and giving the right amount of power to the rotor. In addition, there is a slip ring end bearing that help the rotor shaft with its rotation.

Alternator Belt or Pulley

An alternator belt or pulley can also disrupt the flow of energy toward the battery. It will ultimately impact the car's performance if your pulley wears down over time. The belt holds the alternator to the engine pulley.

In case the belt starts to loosen up or break, the alternator will not transmit any power to the battery. Thus, it will cause the battery voltage to go down. The issue of belts is not very common and usually occurs in old cars with a rebuilt alternator.


Although it is not common in old vehicles, the new ones have a controller(computer) that controls the alternator digitally. It helps you keep a check and balance on the alternator's operations. But, this is something not common in various automobiles.

Role of an Altenator in the Vehicle's Electrical System

If you look at the car's electrical system, you find three major elements:

  • Battery

  • Alternator

  • Voltage regulator

These are vital parts of the car's electrical systems. The alternator generates the electricity with the help of a battery to power up vehicle components, including air conditioning, and other accessories. Here is what the role of an alternator is in the car's electrical system:

  • Alternator's primary responsibility is to charge the battery so that the vital elements in the vehicle can be powered.

  • It charges the battery, which provides enough electricity to start the car.

  • When you drive the car, the alternator will produce energy and send it to the battery and the electrical system.

How Does the Alternator Use Mechanical Energy?

The battery plays a vital role when you put your key in the ignition switch to start it. On the other hand, the car alternator keeps it alive when the engine runs. It provides power to the car's other electronic components, including:

  • Dashboard instruments

  • Electric steering

  • Lights

  • Heated seats

  • Power windows

  • Radio

  • Windshield wipers

The alternator's primary function is to supply these elements with direct current (DC) power. In addition, it also charges the car's battery when you are driving. Moreover, the alternator generates the AC currents that it converts to DC. This current is stored for the battery to use in the future.

The mechanical energy is converted to electrical energy by the alternator. Once you turn your engine on, it powers the drive belt attached to the alternator. As a result, the pulley turns the rotor shaft and causes a set of magnets to spin around the coil.

The spinning magnets produce alternating current (AC), but the car's electrical elements need the direct current (DC) to operate. The DC is a kind of electricity that lets the electrons flow in just one way. Therefore, the alternating current goes through the rectifier, which converts AC current into DC.

The alternator's output voltage also has a link car's speed, so it uses a regulator to control and maintain a constant output.

If your alternator is working fine, it will charge the battery and ensure all the accessories in your vehicle run properly. However, if the case is vice versa, it will not charge the battery, and you will face difficulty with the various electrical elements.

Why Is An Alternator Crucial Part in Your Car?

If you want to enjoy a pleasant driving experience, you need to check that all the parts operate efficiently. Since the alternator plays a critical role in starting your vehicle, you need to check it beforehand. The alternator not only charges your battery but also ensures other critical electric components are working fine.

Though most cars come with an alternator, hybrid vehicles don't have one. Instead, they use a DC-to-DC converter to recharge the battery. If you hear any strange noises, it is better to get your car checked immediately. A professional car technician can have a look at it and get the issue resolved.

Usually, most alternators are not so heavy and are as big as a count. Since an alternator housing is made from aluminum, it allows them to be light in weight. Most importantly, aluminum plays a critical role in dispelling the heat that comes from electrical current.

The generator function in the alternate can only work if you can keep the heat low. Therefore, you will find cooling fans in newer alternators. The old car alternators had external fan blades behind the pulley near the rotor shaft to reduce the heat. In addition, you can also find the vents that scatter the heat on the front and back of the car alternator.

A car alternator will have many terminals at the back. These terminals are the connection points for the electrical current and do multiple functions, such as:

  • Bypassing the regulator

  • Closing the circuit to the warning lamp

  • Monitoring the battery voltage

  • Turning the voltage regulator on to connect it with the battery

How To Ensure Your Alternator Stays in Working Condition?

The alternator has a certain life span that is greater than a car battery. However, you need to take proper care of it to ensure it stays in working condition. If you don't focus on maintenance, it will start to wear off quickly. Since the alternator comprises parts that continuously move, it gets dirty.

The dirt can pile up on it and cause various issues. Also, the alternator can start to wear out in extreme weather conditions. So, if you live in an area with high or low temperatures throughout the year, you need to ensure proper maintenance of the alternator.

The most common way to find out if your alternator is wearing out is when its bearings fail. The failure of bearings will ofter create a loud and unpleasant sound. If you experience any such noises from your car, you need to get it checked by a mechanic.

What Happens if Your Car's Alternators Start Dying?

Alternators are a kind of generator that produces AC current. They are not complicated parts that you will find difficult to understand. The essential thing to keep in mind is that if the alternator dies out, your car will not move from one place because you won't be able to drive it.

Since the alternator won't charge the battery, it won't be possible for you to drive it. You will need a tow truck to get the car to the mechanic.

If your alternator is not working properly, you might encounter some problems. It is best to note any issues with the car's components since they might indicate an alternator problem.

Signs Of a Faulty Alternator

The alternator is a much more durable part than a battery. It has a life span of about 8 to 9 years, depending on various factors. Nevertheless, over time it will malfunction, and you would have to look at options to get it fixed. Here are some signs that can help you identify a faulty alternator.

Frequent Problems with Electrical Accessories

Most often, people that have a faulty alternator will witness problems with the electrical accessories in their car. The car's windshield wipers, power seats, windows, and other electrical components will not operate as efficiently as they did. Since these components don't receive sufficient energy, they don't work properly.

The headlights will not work as they did, and you will face other issues too. So, if you face any problem with your electrical appliance, you should pay attention to it. It is an indication that your indicator is not working properly and needs to be fixed.

Strange Sound or Odor

Another thing that signals a problem with your car's alternator is any strange sound or smell. You will hear whining noise coming from under the hood. The cause of this noise is that the drive belt is misaligned, and it rubs against the pulley. As a result, you will hear a growling sound.

There is a chance you can smell a strange odor, similar to burning rubber. The heat from the engine might cause the drive belt to wear down. Consequently, you will have to endure an unpleasant odor in your vehicle. There is also a possibility that this smell is due to any frayed wires in the alternator.

Issues with Headlights

While headlight issues can also be due to a problem with the battery, it also signals a potential issue with the alternator. As soon as the alternator starts to die out, it won't supply the same amount of energy to the electronic accessories in your car. So, you might see a dip in the performance of a few functions, such as headlights.

Your headlights can either under-perform or over-perform as the current to the light will fluctuate. The headlights won't receive a constant voltage flow, and it might also cause them to go dim or bright. These signs indicate a problem with your car's alternator, and you should get it checked.

Difficulty Starting or Staying On

Once the alternator starts to fail, you might encounter problems when you start your car. If it doesn't stay on after you start it, then there is a good chance that your alternator is failing. The battery won't get recharged when you are driving your car.

Therefore, you will face difficulty when you start the car. The battery won't receive sufficient energy and will deplete quickly. People can find it difficult to determine whether there is an issue with their batteries or the alternator. So, the best way to find out is by jumpstarting your car.

If you jumpstart your car and it continues to run without any issues, you need to replace the battery. Whereas, if the car does not stay on for a long time and dies out shortly, it indicates an issue with your alternator. The jumpstart test is an easy way to determine which critical component of your automobile's electrical system is faulty.

Cost of Replacing an Alternator

The cost of an alternator will depend on various factors, such as make, model, size, etc. You will have to check with your mechanic to know the exact cost that you will incur for a new alternator. Usually, it can cost you anywhere from $350 to $400 to replace a faulty one.

Summary of the Entire Process

It can be difficult for people to understand the alternator's process that doesn't have a good grasp of the technical terms. Here is a summary that explains the entire process in simple words:

  • When you turn on your engine, it will power the drive belt and cause the pulley to turn the rotor shaft.

  • It will provide a magnetic field that will generate AC

  • The AC will go through the rectifier, which will convert it into DC.

Getting your car alternator checked from time to time is vital to ensure it continues to operate as before. If you can maintain it, you won't have to worry about your alternator for 7 to 10 years. The signs in this article will help you identify the issues under the hood.

Also, many car dashboards have an indicator to notify you about any possible issues with the alternator. You can check the dashboard light to know about any issues with your alternator. If you feel there is any problem with your car's alternator, you can visit an auto service shop.

The technician can check if the alternator gives enough energy to all the components. They will also let you know about the repair and replacement options if your alternator fails. You can get it repaired, rebuilt, or remanufactured. It is better to consult with your technician to know the best option for you.