A car’s alternator is one of the most important parts of the vehicle. While your battery is what starts your car, the alternator is used to recharge and keep the battery running. The alternator also powers the rest of your electrical systems, such as lighting or air conditioning, while your engine is running. The alternator transforms mechanical energy generated by the engine into electrical energy used to power those electrical components of your car as you drive.

So we’ve briefly looked at what the alternator does, how it does it, and why it’s essential to the proper functioning of your car. Now let’s take a closer look at how it works in more detail.


The parts that make up an alternator and what they do are:

The serpentine belt

receives the mechanical force from the engine.

The voltage regulator

ensures the correct voltage output of the alternator and is what provides power to the rest of the vehicle.

The diode rectifier

transforms the AC current produced by the alternator into DC that the car can actually use. 

The stator

is a fixed ring in the alternator lined with copper wire. This part provides the electromagnetic energy that makes the rotor spin.

The rotor,

also known as a rotating magnetic core or flywheel, is the moving part of the alternator, consisting of an electromagnet that spins at high speed around the stator due to the stator’s magnetic field. The combination of these two parts generates the electrical current used in your car.

The cooling fan

does exactly what you’d imagine – alternators get hot, and the cooling fan helps them cool down.

Knowing each of your alternator’s components makes it easier to understand how it works. Simply put, the alternator exploits the engine’s rotation and its connection through a belt to transform said rotation (mechanical energy) into electrical energy used by the battery to power the various electronic systems.


As a general rule, turning the key in your car’s ignition should cause the process described above to take place. The dashboard lights should turn on, letting you know that everything is in working condition and that the current generated by the alternator is reaching your electrical systems.

However, on other occasions, one of the panel lights might stay on and point out something is wrong. In this case, you need to evaluate the signs that your car is showing you to know if it is the alternator that is not working properly. Among the signs that indicate faulty car alternators are:

Instrument panel warning light on

Without a doubt, this is the simplest sign to see. If the alternator light (if your car has one) or the battery light is on, something is likely wrong with your alternator.

Low battery

This light will warn you if your battery is low on charge, which be caused by a faulty alternator. To find out if it is a battery or alternator problem, be sure to stop in at the Service Centre and we can check for you and fix any problems you might have.

Unusual noises

If you hear a grinding or whining sound, this could indicate that your alternator is not functioning properly. 

Failures of electronic systems

If the car alternator is not in optimal condition, the battery will not charge properly and can be discharged over time, leading to your car not being able to start. On top of this, if you notice any of the lights in your car are dim or that any of the other electrical components are wigging out, then you might have a problem with your alternator!


If you think you have a problem with your alternator, then be sure to stop in at The Service Centre, and we can get it replaced for you. We are leading mechanics in the Thornton & Maitland area, and we provide the best service for your vehicle, whatever the make. 


If you prefer, we can also repair your car alternator. This takes a little bit longer to do than simply replacing it, but is usually a bit cheaper. Just let us know what you’d like to do when you come into The Service Centre, and we can make sure to work to your specifications.


Replacing your car alternator is a non-trivial operation requiring expert mechanical knowledge.

Our recommendation is always to turn to professionals and experts who evaluate the state and condition of your vehicle, especially when it comes to such an important mechanical part. At The Service Centre, our qualified professionals are always ready to advise you on any breakdowns of your vehicle.

The Service Centre is a group of workshops focusing on providing quality car servicing, maintenance, and repairs to our customers in Newcastle & the Hunter Valley Region, with workshops in Maitland and Thornton.