What Does an Alternator Do in a Car – Functions & Symptoms

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what does an alternator do in a car’s engine exactly, the function of an alternator is to generate electrical power by converting mechanical energy. This device, which is usually mounted on the engine, is used to keep the battery charged and power electrical components in a car.

For example, the headlight, air condition, warm seats even your cars battery depends on the alternator to stay alive and functioning. One other important function of an alternator, is “continues production of electrical current” to keep the battery charged and healthy.

Function of Car Alternator


Alternators are electrical generators that convert mechanical energy into electricity. They generate electricity to power your car’s electronics and accessories as well as to charge the battery.

The explanation should should have given you a little bite of answer on the question “what does an alternator do“. The alternator can gets spoilt or even case to work entirely over time and this means your car’s electrical components are at risk.

Below are a list of the major functions

  1. Charging of the car battery.
  2. Provision of electrical current to car accessories including
    • Radio.
    • Heater.
    • Air condition.
    • Headlights.
    • Massaging and Seat warmers.

An alternator normally has three connections: positive (+), negative (-), and ground (GND). The big questions now is, what are the symptoms of a bad alternator Continue reading to find out.

Read Also:- How Long Will a Battery Last with a Bad Alternator

Symptoms of a Bad Alternator?

Now that you have understand what and alternator is and how it works, its time to know What are the symptoms of a bad alternator. How do you know when your alternator needs to be replaced or when it starts being faulty.

Well you don’t need to consult any specialist to know if you alternator is misbehaving. Let me work you through how the alternator works again just for you have a very good picture of how easy it is to tell if you have a bad alternator.

  • Weak or a dead Battery

A weak or dead battery means your would not start because there is not power to ignite the engine. If you remember well i mentioned before that the cars battery is only needed to star the car, that is why wen u have a bad battery then yo have to jump start your car.

If your car’s battery keeps becoming week or dead there is a big chance that your alternator is not working or is faulty. Recall that what the alternator does in your car is keeping your battery charged and other electronic components working.

When your cars alternator is dies, then a lot of things can can start misbehaving very fast in your car. Your battery no matter how new it is, it is bound to start giving your problems when starting your car and will eventually die if the alternator is not replaced in time.

  • Battery Light On dashboard

Your cars dashboard is packed with a lot of signs and indicators connected from inside the cars computer. These signs and indicators helps you to know when your car needs some certain care and repair, they also help you drive safely.

Among these dashboard sign includes a small battery sign indicated with ALT or GEN. When you cars alternator gets faulty the battery sign in the dashboard is an early sign you would see on the dashboard.

  • Grinding or Whining Noise from pully belts

Bearings, the stator and rotor, and other components that are spinning inside the alternator to create the energy can begin to fail and produce whining or grinding sounds.

  • Disturbing Smell from pully belts

Disturbing and very unpleasant smell tends to start to emit from the cars. This smell is caused by failure from the alternator’s robber belts to rotate normally thereby creating friction which brings about the unpleasant smell from the cars alternator.

Now that you have known what an alternator does in a car, how the alternator works and signs and symptoms of a bad alternator, lets see other things to the alternator.

Read Also

How to Check if Car Battery is Bad 3 Simple Steps

How to Reset Service Battery Charging System Light


How does the alternator charge the battery

Your car’s does a mechanical work of converting mechanical energy into electrical energy. Whenever you start your car the engine turns and powers a drive belt that rests on a pulley attached to the alternator.

The alternator’s rotor shaft is turns and keeps turning by the pulley which spins a set of magnets around a coil. These spinning magnets generate alternating current (AC) around the coil, which is then channeled to the alternator’s rectifier. The rectifier converts that AC power into DC power, which activates your car’s electrical systems.

Now that you have the exact picture of how and what the alternator does in the car lets see the faults. What are the symptoms of a bad alternator, Good question, there are few signs and indicators that your alternator needs replacement.

What Are The Risks Of driving With a Bad Alternator

There are not much risks in driving with a bad alternator but am sure You don’t your car to stop half way in the woods or on your way to work. Well i guess not much since the risk is not life threatening right but am sure you hate disappointment too.

To avoid getting disappointed by your car in the middle of no where in the woods then you should not drive with a dead alternator. If you do risk to drive with a deal alternator then your car would not go far before it dies and your cars battery will die too no matter how new it is.

A friend of mine last week was narrating his experience to me about huis car alternator he said “I just replaced my battery and at first it would still run, then sounded lumpy, then wouldn’t start, then wouldn’t jump start then i gave up. This was all in the space of about 10miles.”

The work of an alternator in your cannot be replaced by any part, so always try to always check for indicators and make sure your alternator is good shape. Remember that the alternator supplies all the cars electronic components of the car with direct current (DC) power. Your alternator is also responsible for charging your car battery while driving.

Can a bad alternator kill a new battery?

The battery is only there to help your car ignite and start the engine in the first place while the alternator does charge the battery subsequently. Your cars alternator is a means of livelihood to the cars battery and other electronic components of the car.

Below is a photo graphic image of how the alternator really works..

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If the alternator does not start the car’s electronic components while you’re driving around or idling, including your headlights, electric steering, power windows, windshield wipers, heated seats, dashboard instruments, and radio. So yes a bad will alternator sure kill a new battery.

Labeled Diagram of Car Alternator

How far can I drive with a dead alternator

How long an alternator can last before you start experiencing issues is not certain as this depends on many factors. Some factors that determine how long includes weather condition and mode of car use.

No one can actually tell how long an alternator can last given the immense function the alternator shoulders. But is certain that a good alternator should last for up to 100,000 miles in reasonable conditions.

However, like i have mentioned before, the whether condition matters a lot when it comes to how long an alternator would serve. In Areas with very high or extreme heat your cars alternator might not stay long in good shape like for others in areas where the whether condition is okay.

Try to constantly look out for symptoms that may be clue you in if the alternator is beginning to fail. You may notice some minor unusual behavior such as:

  • Flickering headlights
  • Dim headlights
  • Difficulty starting the car

Other times, there may be more obvious symptoms that the alternator is struggling, indicating that the electrical system will need to be tested. Remember, what an alternator does in the car car is provision of current to electronic components, so, always endeavor to look out for indicators of a bad or faulty alternator


The alternator has an important function in the car, it generates the necessary power to start the engine and recharge battery under idle conditions. The alternator is a mechanical device that converts mechanical energy into electrical energy.

Its function is to generate electricity to power other electrical units of the car such as headlights, radio, ignition system and air-conditioning compressor. The alternator turns at a speed of up to 14,000 rpm when running at full capacity.

This process takes place when the engine is running and produces an output voltage relative to engine RPM. The current produced by alternator can be boosted by using a belt driven or direct-driven system, which will produce more power for higher load items such as headlights or air conditioning compressor.

So finally, this article has attempted to answer the question “what does and alternator does in a car” by highlighting the functions or function of an alternator in car engine. For any questions and unclarified please use the comments box to ask.

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