What is An Alternator in a Car? and How Does it Work?

What is an alternator in a car? –-> The alternator is an element of the automobile’s electric circuit. It transforms mechanical energy into electricity and provides electrical power while the vehicle is in motion.


A bad alternator can cause voltage spikes or generate insufficient voltage. It is essential to repair it because, in the long run, it can cause problems in the electrical system and the electronics of the car.

The operating principle is relatively simple: the alternator is a device that, when turning, generates an alternating current inside it through electromagnetic induction; to turn, the alternator is connected to the engine through the service belt. 

Slow operation of Some Electrical Elements

When an alternator is malfunctioning, it is not generating the proper voltage – or current intensity – to supply power to the car’s electrical systems. Some of them may work partially or work more slowly. Another common symptom is usually a slower than usual operation of the power windows or low intensity of illumination of the headlights. At the same time, some systems may stop working or stop working intermittently. A bad alternator can cause these types of random and sporadic failures.

Squeaks and Groans Coming from the Alternator

Another symptom that the alternator of our car is not working well is squeaks and groans coming from it. These can cause by a worn or bad accessory belt – the pulley that connects it to the car’s crankshaft – or they can come from the alternator itself, indicating a fault in its moving parts or bearings. In a more advanced state of deterioration, a failed alternator does not correctly charge the car’s battery. As a result, our battery is discharged, and one day we will even be able to start the vehicle. While a bad battery usually causes this situation, it can also be caused by a bad alternator.

Currently, vehicles incorporate a large number of components that require electrical power. If not for the current alternators, many of these systems would not function properly, as they have very demanding electrical needs.

What is An Alternator in a Car? The Alternator is Made Up of:

what is an alternator in a car


It is the one that receives mechanical force from the thermal combustion engine via a belt, usually poly V. It also controls the movement of the rotor inside and the fan inside the new generation alternators.

Rotor (inductor): it

It is the mobile part of the alternator. An electromagnet forms it that receives current from the regulator through slip rings located on the shaft. This electromagnet produces a magnetic field to which the stator coils (fixed part) react, producing electric current.


Maintains a maximum alternator output voltage of 14.5 volts and regulates the amps needed by the battery.

Stator (armature): 

The fixed part on which the three-phase winding is located. It can be in the form of a star or a triangle.

The diode rectifier bridge is the element in charge of rectifying the alternator’s output current (since it is alternating), making it continuous and feasible for the car.

Five Things that Give Away Problems in the Alternator

Before drawing any conclusions, certain signs will indicate that the alternator is failing :

Headlights are dim or flickering because the alternator is not generating enough power to power the electrical system. On the other hand, if the headlights are bright, they are okay no matter how fast the engine is. 

Electrical components not fully functional

The player, raising or lowering power windows, clocks, seats, or any other electrical accessories inside the vehicle may stop working correctly because they do not receive the amount of electrical current necessary for their operation. 

Battery drains fast

Another of the signs that your vehicle gives you when the alternator is being damaged is that the battery does not charge 100%, which could cause it to be damaged in the long run, and have an abrupt start. 

Strange noises

Different sounds indicate that one of its parts or the entire alternator is failing, so you have to be very attentive to grinding, howling, or some other strange noise that your car makes when rolling.

Alternator FAQ

what is an alternator in a car

How does the alternator work?

The alternator produces alternating current, which it obtains through a drive mechanism driven by a combustion engine. In other words, the alternator works to the rotation of the combustion engine, generally through a belt.

What is the Alternator for?

The electrical systems of a conventional car work at a voltage of 12 volts. We are talking about all the car’s electrical systems, such as the electronic control unit, the infotainment system, or the car lights. These systems draw power from the car’s 12-volt battery when the engine is off, slowly discharging it. When we start the engine, it is supplied directly by the alternator, which at the same time recharges it.

Without an alternator, the 12-volt battery would need to be restored externally.
Cars with a 48-volt electrical system do not have an alternator: they have a power generator connected to a high-voltage battery. This intelligent – and reversible – alternator also acts as a starter motor and electricity generator and assists the thermal engine at specific moments, pouring power into its crankshaft. These electric machines replace both the conventional alternator and starter motor.

How much does it cost to replace a car alternator? What is the cost of an alternator in a car? How much does it cost to get the alternator replaced? How much does replacing an alternator cost?

You should budget between $500 and 1,000 for a replacement alternator.

How much is alternator repair?

Alternator repair costs estimated between $100 and $170

How much is an alternator for a ford focus?

Around $100 and parts price is $ 350

What is a car alternator?

The car’s alternator is one of the critical parts in its correct operation. It is responsible for converting the engine’s mechanical energy into energy for its electrical systems

The battery won’t recharge with a bad alternator, the car may not start, and many of its essential systems – such as lighting or climate control – won’t work. In modern cars, the same will happen with all systems that depend on electronics – which today is practically all. 
It’s hard to tell if an alternator is working correctly. If you have no idea how to check it, it is easiest to test it with a voltmeter. If you know your car well, you could use a few methods. This test gives you a general idea of ​​the car’s condition and the battery. Some newer vehicles have built-in computer-controlled charging systems and may require further testing.

How do you test your alternator?

Check the battery first: 
it is necessary to start the vehicle, which, in turn, turns the alternator at an adequate speed to keep the battery charged. This means that if your battery is low, you won’t start the vehicle. Therefore you won’t be able to test the alternator either, rendering any other voltmeter tests useless. If it’s cold outside or your battery is old, the problem may be the battery itself. That is why you need to check the battery before everything.

How to do it?

Turn off the engine: You must make sure your engine is off before connecting the voltmeter.
Open the hood – > Connect the voltmeter to the battery: connect the voltmeter’s red terminal to your battery’s positive terminal and the black terminal to the negative terminal. Prevent your skin from coming into contact with the battery

Look at the voltmeter: if the battery shows a measurement greater than 12.2 volts, it means that it has enough charge to start the alternator and test it consecutively with the voltmeter.

If the battery does not have enough voltage, you can recharge the battery and re-measuring it or try a different method of testing the alternator.
Start the vehicle and increase the revolutions up to 2000 RPM. 
This will draw power from your battery, causing the voltage regulator to force the alternator to work at full throttle.

Keep the engine running and measure the battery again with the voltmeter. 
When you see the measurement this time, the voltage should go up to 13 Volts. If the variation in revolutions per minute causes the voltage to fluctuate between 13 and 14.5 Volts, it means that your alternator is in good condition. On the other hand, if the voltage remains the same or decreases, it means that your alternator is not working correctly.

Repeat the same process, but now with the lights, radio, and air conditioning. 
If the battery voltage stays at 13 volts with the engine at 2000 rpm and all accessories, the alternator charges the battery.

How to repair a car alternator?

To repair the alternator of your vehicle, you must check the different parts of it; you must do the following:

In the first place, you must check the alternator rotor with the tips of a tester. We measure the continuity of the coil. If we do not have a signal, the coil may be damaged and should be replaced, on the other hand. You can verify that the coil does not have a short or ground. This is done when we measure continuity between the coil and the alternator.

Test the alternator coils:  Measure the coil terminals and its core with the tester. If we have a reading, the coil is going to the ground. You must ensure that there is no continuity between these two components.}

Test the bridge: connect the tip of the voltmeter to the support plate of the rectifier bridge and connect the other tip to the terminals. If it gives you a reading close to zero, it means that the diode is fine. Otherwise, you have problems with the diode.
Verification of the brushes: check that the brush slides on the support and that the current cable is correctly connected. The tester measures if it has continuity with the terminal and the brush.

How to change the alternator of your car?

· The main step is to disconnect or remove the positive cable from your car’s battery.
· Locate your car’s alternator.
· Using a unique tool, loosen and remove the belt from the alternator pulley.
· You must remove the screws that hold the alternator to the vehicle’s engine. These screws can be from 2 to 4 depending on the make of the car.
· Now, yes, remove the alternator and the nut for the electrical connections
· Once you have the complete alternator in your hands, you can go to a specialized mechanical store to acquire the new alternator that matches its characteristics with the old one.
· Once you have purchased the new alternator, you must place it by doing the following: connect the electricity cables to the new alternator, place the alternator in the correct position with its proper screws, place the pulley making sure it is in line with the belt, pass the belt through the alternator pulley, and finally connect the positive battery cable.
· Proceed by starting the vehicle and ensure the new alternator is charging.
· The cost of an alternator is represented by the manufacturer’s brand and its quality.

Why Is My Car’s Alternator Failing?

It often happens that the car battery discharges regularly and easily, this may be due to the alternator being damaged, but could you repair it yourself? The answer is YES, and then we will be explaining the steps you must follow to repair your vehicle’s alternator.

Clarified this point, we proceed to tell you to repair your car’s alternator.
Before disassembling the alternator of your vehicle, you must have the following essential knowledge to do so:
· You should know what the parts that make up an alternator are. 
· To disassemble the alternator, you must know where the engine bands, the power, and the alternator are located.
· Once the alternator has been disassembled, only the metal parts of the said part should be rinsed with gasoline.
· The regulator, which is one of the parts of the alternator, is often found outside the alternator or one side of the engine body.
· You should know that the replaceable parts in your alternator are: the regulator, the diodes, brushes, capacitor, the bearing (both sides), among others.
· You should generally replace these parts because the other parts may not work with the same performance if you only change the regulator.

What does the alternator do in a car?

When inserting the key in the ignition and turning it, the alternator rotor coil receives current from the battery. Once we start the engine, the rotor coil begins to rotate and goes from receiving energy to generating it. In this simple way, it becomes self-sufficient. It provides the necessary energy to meet the demand of the systems that facilitate driving and life on board the car, such as the air conditioning, the power steering, or the audio system.

If the alternator is working correctly, the light on the instrument panel will go off. If, after starting the car, the light does not go out, it could indicate that the alternator is not providing power to the auxiliary systems. If so, it will be necessary to check that the 12 volts from the battery reach the regulator’s input and that the diodes of the rectifier bridge are not in poor condition. In addition, it could also happen that the slip ring brushes are in poor condition, and therefore the necessary current would not reach the rotor.

How long does it take to change an alternator?

Around 2 to 3 hour

What does an alternator do?

The alternator is the element of the automobile’s electrical circuit whose mission is to transform mechanical energy into electrical energy.

How much for a new alternator?

$400 to $1000

How much does an alternator belt cost?

Belt costs $ 20 to $80
The labor cost would be $100

Where can I buy an alternator cheap?

New DB Electrical Alternator is the best that you can buy from Amazon.

How much is an alternator for a Hyundai sonata?

 $450 to $900 and labor cost $130

How to remove the alternator?

1. Disconnect the car battery.
2. Loosen the bolt and slide it off the pulley.
3. Remove the bolts that attach the alternator to the vehicle’s engine.
4. Disconnect the cables from the alternator, trying to remember how they were fixed later.
5. With the help of a vise (an object used to hold mechanical parts more comfortably and professionally), and the respective wrenches (English and Allen), remove the nut that holds the pulley to the fan.
6. To remove the pulley, use the mechanical puller, which will make this step much easier for you.
7. Remove the screws that join the cover where the pulley is located to the outer frame of the diode.
8. Lastly, remove all the alternator parts like the diode pack, bearings, bushings, etc. Put them aside, controlling the order of placement of each of them.

Where to buy alternator bearings?

You can buy it from Amazon. We recommended 

DB Electrical 400-44119 New Alternator

How much is a new alternator belt?

Around $12, for more information, click here.

What size alternator do you need for car audio?

To calculate the capacity or amperage you need the alternator to deliver, determine how much extra power the audio system demands in addition to the current system.

The easiest way to calculate that figure is to use amps x volts = watts. For example, installing a 2,000-watt amplifier, assuming a nominal voltage of 13.5V, will add approximately 150 amps of demand to the electrical system. Also, calculate how much amperage the rest of the car draws and add it to the sound system.

The total amps you get will be a rough estimate of the car’s maximum draw and indicates the size of alternator you’ll need (measured in amps). It’s best to have it calculated by a professional, as every car and sound system is different. These figures also do not consider the difference in power produced at the engine’s different RPMs (revolutions per minute).

Does your audio system need a bigger alternator?

The easiest solution is to keep the volume at a level that the alternator can handle. But if you want a powerful sound to go along with your power amp, you have a couple of options.
First, install a booster capacitor. This is similar to a battery because it stores electric charges through conductive plates. A charging system cannot provide more power than it is intended for. Subwoofers can be a problem because they require more energy to produce low frequencies.
A booster cap allows a car’s amplifier to operate at higher output levels by providing a reserve reservoir of emergency power.

But a capacitor is only a viable solution if you experience flickering lights or decreased bass response at high volumes. The boost capacitor won’t do the trick if it draws too much power at low or medium volumes.
A high-power alternator is the best solution in most cases. Although it is an expensive option, it will ensure that your high-performance audio system has the power it requires without compromising your car’s electronics.

What size alternator do I need for car audio?

More power is better for car audio and vice versa. A great amp and subwoofer are essential if you want your music loud and clear with a great bass response.
The alternator is responsible for producing all this power. The alternator is the engine’s component that charges and runs the electrical system. Factory alternators are not built to handle high-fi sounds. The car will react if you add a powerful amp to it without making any power adjustments. It is usually visible as dimming headlights and flickering dashboard lights

How to rebuild a car alternator?

· First, check the alternator rotor, measuring the continuity of the coil with the tips of a tester, and if there is no signal, the coil may be damaged and should be replaced.
· Also, verify that the coil is not shorted or grounded by measuring the continuity between the coil and the alternator.
· Test the alternator coils by measuring the coil terminals and core with the tester. If there is a reading, it means that the coil is grounded, so you must make sure that there is no continuity between these two components.
· Test the bridge by connecting the voltmeter lead to the bridge rectifier support plate and connecting the other lead to the terminals. If there is a reading close to zero, the diode is suitable. Otherwise, you have problems in the diode.
· Check that the brushes slide on the holder and that the power cable is correctly connected. Measure with the tester. There is continuity with the terminal and the brush.

Why does the alternator fail?

One of the most common causes of low or no charging output from the alternator is one or more faulty diodes on the back of the alternator. There are three pairs of diodes (6 total) in the “rectifier” assembly that convert the Alternating Current (AC) output of the alternator to Direct Current (DC).

How to test for a bad alternator?

1. Dim lights The faulty alternator symptom that most drivers recognize is dim or flickering lights.
2. Service engine light.
3. Strange noises. 
4. Electric problems. 
5. Engine stop. 
6. Dead battery.

How long does a car alternator last?

Around 100,000 miles

What type of alternator do I need?

Equal to 25% (lead acid) 
30% (gel) or 45% (AGM) of your total battery capacity