what is an alternator in a car

What is an alternator in a car? – How does it work?

There are some parts of your car that are so essential to the functionality of the car or vehicle. Most times, they determine if the car will start and if all other components in the car will operate optimally. One of them is the alternator and what is an alternator in a car?

The alternator in a car is responsible for the electrical power in your car. It converts mechanical energy (rotating the engine) into electrical power to keep your battery charged, and other operation components like lights, radio, and all powered. 

If you find it hard to start your car or you notice that the battery runs down with no power to get the car to work, it is an indication that your car alternator is not working rightly. It’s the work of the alternator to keep the battery up with charges to run the car and if it doesn’t, the car will get stuck.

What is an alternator?

what is an alternator in a car

An alternator is a term used to refer to a part of the car’s electrical system. It is one of the most important parts of your vehicle. Without it, you may not be able to run your accessories including your radio, power windows, and lights when driving at night.

Also, it helps to convert mechanical energy into electrical energy. The main parts of an alternator include the rotor, stator, and commutator. It helps to keep the car battery with the right charges needed to power the car. It helps to ensure the battery does not run out of charge at all.

What is an alternator in a car?

The alternator is one of the most important parts of your car that not many people consider but you need it to run fully. The alternator keeps the battery charged, turns it into voltage so the car can run. Without it, the battery would die and you wouldn’t be able to turn on the lights or radio, and best of all, you couldn’t start the car.

The alternator belt spins at a very fast speed which provides its voltage. This makes sure that there is enough power in the battery and that all accessories are operating properly, such as headlights, and interior light.

In the days when car engines revolved around generators, alternators were occasionally used for changing mechanical energy into electrical energy. It was easier to construct a generator that could be run off the engine to provide electrical power for the car than it was to devise an electrical generator with torque characteristics identical to those of the engine.

Nowadays, however, nobody uses generators as alternators because they aren’t a very safe way to produce high voltage electricity.

Alternator vs generator

Automotive alternators and generators are both electrical machines that convert mechanical energy into electric energy. That’s where the similarities end. Both have moving parts, but they’re used in different ways and power different systems.

A generator is a lot like an alternator in that they both produce electricity, but there are some major differences you should know about. Generators utilize fossil fuels like propane or gasoline to produce energy. Alternators use electronics to convert rotational energy into electricity. To put it simply, generators create gas and alternators create electrons.

Car alternator problems / Alternator symptoms

Car alternator issues can occur for a number of reasons, but the most common cause is an alternator that is not working properly. Common signs include dim lights, the car stalling, or standing on the side of the road. If you have car alternator problems, don’t just put up with it, get it checked out by a professional today.

  • Dim or too bright light

If your headlights seem brighter or dimmer than usual, your car alternator may be out of balance. Leaning heavily on one light may cause overheating and can result in additional stress on the alternator and battery. Usually, this problem will correct itself once you adjust the lights and return them to an equal load or eliminate the uneven loading.

  • Dead battery

Your car’s alternator provides energy to run car electrical components as well as charge your battery. A bad alternator can lead to a dead battery and even damage the rest of the vehicle’s electronics including the engine computer.

Once that happens, you sure will find it hard to start the car and might have to jumpstart using NOCO Boost HD GB70 2000 Amp 12-Volt UltraSafe Lithium Jump Starter to revive the battery. Once it gets the charge, you might want to run the car for a while to ensure the battery is back to its usual condition.

If the method of jump-starting doesn’t work, you might have to get a new battery that is if the alternator has damaged it beyond repair.

  • Slow or malfunctioning accessories

Your car’s engine alternator supplies electricity to the battery, and all of your vehicle’s accessory systems such as power windows, powered seats, headlights, taillights, radio, and much more.

If you notice your accessories are running slow or not operating properly, start with having your battery tested for sufficient voltage. The next step would be to have an experienced technician inspect your charging system performance.

  • Trouble starting the car

It’s not always easy to spot a bad alternator, but when you do, the signs may be hard to miss. First, if you notice trouble starting your car, or if the battery continues to run down even when the car isn’t being driven, you may have a problem with your charging system and a failing alternator.

If the voltmeter gives off a reading of no more than 12 volts at idle and under load, then it’s likely that your alternator is getting faulty.

Also, if you are having trouble starting your car, especially when it’s warm outside, check to see if the alternator is faulty. It may be making a bad clicking or buzzing noise, or there may be no noise at all. To diagnose this problem, you should have your car checked by a mechanic.

  • Growling or whining noises

If you hear growling or whining noises from under your hood when the engine is running it could be a sign that your alternator is going out. This device takes energy from the engine’s power and converts it into electricity for the battery, steering, and other electrical systems. So, such noise could be a clear sign that the alternator is bad.

  • The smell of burning wire

There are a few signs that warn you if your alternator is failing. The first sign is the smell of burning wire, especially when you turn your engine on. If you don’t know what the smell of wire burning is like then ask someone well versed with vehicles. Another sign that you should look out for is that some electrical appliances in your car will not run because they are not getting electricity from the car battery.

  • Battery light on the dashboard

If you see the battery warning light on your dashboard, you’ll need to have your alternator checked by a professional. It’s important to let the light go off before driving, as driving with the light on may damage other vital engine components.

If your battery loses power each time you start your car or the warning light flickers stay on, you may have a problem with your alternator. Alternators keep your car’s electrical system running, so your battery and other electronics are constantly getting power from it.

Alternator how it works?

alternator how it works?

The alternator converts mechanical energy into electrical energy. The electrons produced by the rotor are attracted toward a wire that runs through the center of the stator, which is a built-in electromagnetic field. To produce more electricity, the engine must rotate at a faster speed.

It is a belt-driven electrical generator that produces 14 volts of electricity at 60 cycles per second and uses the serpentine accessory drive belt to power the electrical components of your car’s engine.

When a car or truck battery is running low, the alternator kicks in automatically to keep it charged. A car’s alternator works as part of an electrical system that also includes a voltage regulator and a battery.

Types of alternators

parts of alternator

There are different types of alternators that you need to know. 

  • Automotive alternator

Automotive alternators are electrical generators. Their purpose is to convert mechanical energy into electrical energy on demand. It is a product that can be used in vehicles, and it is often used on trucks, tractors, and some passenger vehicles, as well as bikes and boats.

The development of this innovative technology was contributed to by several scientific discoveries in the 1900s. The early history of alternators is marked with many technical developments, leading up to today’s modern technology.

  • Marine alternator

Marine alternators are crucial for keeping your boat’s batteries charged, as well as for running electronics such as stereo systems and navigation devices. If you want to run these devices on your boat, you need a top-of-the-line marine alternator that can handle the load.

  • Diesel-electric locomotive alternators

A diesel-electric locomotive alternator is a device that converts mechanical energy (chassis turnings) into electric energy (alternating current at 50 Hz or 60 Hz), to be used for traction and auxiliary power in a diesel-electric railway locomotive or other vehicles.

  • Brushless alternators

Brushless alternators are used on the vast majority of vehicles today and for good reason. They’re far more reliable and efficient than their predecessors, and brushless motors can be controlled with a great deal more precision than brushed motors.

The brushless alternators are electrical generators. The standard alternator contains brushes (brass or carbon) and slips rings that require periodic replacing for maintenance, which is very challenging in the field with limited tools.

However, brushless alternators do not contain these mechanical contacts, so there is no brush to wear out, greatly extending their life and reducing the amount of work required by maintenance staff.

  • Radio alternators

Radio alternators are an early form of alternator that was used before the introduction of permanent magnet alternators. These rely on a spinning metal disc alternately connected to the high voltage and a winding as the rotor in a simple spark-excited oscillator circuit.

Parts of alternator

You only get to know more about the alternator when you are familiar with its parts and their functions. Below are parts of the alternator and how it operates.

  • Regulator

The regulator serves as the heart of an alternator. It releases energy from the magnet at the right time so that engine can receive a steady stream of juice. Without it, energy isn’t produced or released steadily. The two-wire type controls voltage and current. The three-wire type also controls rotation speed and starts the engine.

  • Rectifier

The rectifier converts the ac to dc by using a series of diodes. The diodes prevent the current from flowing back into the alternator. Rectifiers are used with generators and alternators, which are used to transmit electrical power when the voltage is too high to send over long distances.

  • Rotor

The most important and expensive part of an alternator is the rotor. It has coils of copper wire that are used to generate current. The iron core allows it to spin inside the float bowl. The major function of the rotor is to produce electricity, through the use of the magnetic effect generated by magnetism for moving electrons within the coil.

  • Slip rings

A Slip ring is a small cylindrical device that rolls on the wire while it carries electric current. Its function is to separate circuits electrically while still allowing transmission of energy to be conducted with no loss. A slip ring is used as an auxiliary contact in many applications where contact must be maintained even though the two conductors carrying current rotate at different speeds.

  • Stator

A stator is the rotating part of an alternator. There are two types of those, the squirrel cage type and wound rotor type. The former has steel pole bars that hold the copper wire coils on it, which are copper wires wound by copper wire. The latter has winding made of aluminum cores with copper wire, which is applied to high RPMs motors.

The stator is the stationary part of an alternator and is made of insulated copper wire wound in coils. Its main function is to construct a magnetic field within which the rotor will be able to spin inside.

Car alternator prices

Ascertaining the price of a car alternator can be quite difficult. However, most outlets will price their auto parts based on the OE or OEM standards. Car parts can range anywhere from $150 to $300 depending upon the quality and options built into it.

How does an alternator work?

Most car owners know the importance of having a working alternator. The basic function of an alternator is to continually produce and maintain a constant output voltage to the battery of your vehicle in such a way that your battery can maintain its charge.

This process is achieved through the use of a diode which regulates the flow of current. In addition to this, an alternator works by producing an electrical field that rotates externally while being driven by a pulley system connected to the crankshaft of your engine.

How does an alternator work diagram

How does an alternator work diagram

How to test alternator?

To test an alternator, you will need an accurate multimeter capable of measuring amps and voltage. You will also need to have a battery (connected to the vehicle) and be able to warm up the vehicle before you start testing.

If the first positive pole on the multimeter reads high or zero voltage and the second negative pole is reading low voltage or high voltage, there is a problem with your alternator. If this is what you see then there are two possible problems with your alternator and they are (1) no power to the alternator (2) bad alternator.

What are the symptoms of a bad alternator?

The alternator’s job is to supply electrical power for the vehicle. A bad alternator may cause several problems, including dim headlights when idling, poor battery charging, and even engine overheating. To test your alternator, remove the positive cable from the battery, and using a multimeter, check the battery voltage with the engine running at idle.

If the reading is below 13.8 volts, you have to replace the alternator. Some other symptoms include a dead battery, dim or too bright light, malfunctioning of the accessories in the car, and many more.

What is the purpose of alternator in a car?

The alternator is a small engine installed in your car as part of the electrical system. It delivers extra voltage to charge the battery and maintain other systems in your vehicle (like the power steering). The alternator is connected to the engine and has a belt that connects to the pulley on your engine’s crankshaft.

Its function is to convert mechanical energy into electrical energy that can be used by electronic devices in your car, as well as power certain engine components such as the cooling fan. The energy produced by your alternator allows you to run electrical devices and accessories such as power windows and headlights when you start the engine.

Can you drive a car with a bad alternator?

Of course, you can. But, what’s bad about a bad alternator? If a car just won’t seem to start, or if the engine races and then suddenly dies on acceleration, or if the lights dim and brighten when you turn on the turn signals and wipers, those are all fairly good indications that something isn’t quite right with your charging system.

However, as most mechanics will tell you, an alternator is not just an accessory for your car. It is one of the most important parts of your car’s charging system, since it provides electricity for all of your electrical components, it is not a good decision for you to drive your car with a bad alternator.

What is the price of alternator?

The price of auto alternators can vary depending on whether they are new or rebuilt, the quantity, and your location. In some cases, dealers may have to order specific parts, necessitating an extra shipping charge.

Also, the parts ordering process carries an inherent risk, but many customers trust their dealers to order a part for them for these reasons. New auto alternators can cost anywhere from $150 to as much as $1,400.

How much does it cost to replace alternator?

The replacement cost for an alternator can vary and often depends on vehicle make and model. On average, it costs approximately $130 to replace an alternator.

Does an alternator charge at idle?

An alternator doesn’t charge at idle. It charges anytime the engine is running, but not necessarily at a full charge rate unless the engine is turning above idle rpm. The higher the engine rpm, the more current/amps available to charge the battery.

Can a car run without an alternator?

No. The alternator is part of the electrical systems of your car and not having it would lead to big problems in your electrical system.

There are some older cars out there that just don’t have an alternator like your classic car from the 1980s, but as far as newer models go, all cars have an alternator.

Your battery runs on power from your alternator when you’re driving and that’s how it charges. So, without it, it might be hard for your car to work optimally.


If you own or drive a car, you need to know what is an alternator in a car. The alternator is a common electrical device found in automobiles. Its sole purpose is to recharge the car battery by converting mechanical rotations generated by the engine into electrical power.

Its primary role is to recharge batteries and provide the power needed to start your car. Most cars today run on a 12-volt system. This means that each battery cell is 12 volts. To get the required amount of power for most cars, you need about 60 cells in series (6 stacks of 12 in series).