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What is an alternator and how does it work?

18th July 2023

If you’re driving an older petrol or diesel car, it’s good to be aware of what an alternator is, and what role it plays in keeping your car moving. If your alternator begins to show signs of wear you might not notice it straight away, and if it does fail you could end up not even being able to start your car! This guide will explain what an alternator does and how it works, so if your alternator does start to go, you’ll be prepared.  

What is an alternator?

The alternator is the part of your vehicle that’s responsible for generating electrical power to charge your car’s battery while the engine is running. Your car’s engine generates rotational power to get your car moving, and a small amount of this power is converted from mechanical energy into electrical energy to give your car electrical power.   


<h2>What does an alternator do?</h2> 

In short, an alternator powers your car’s battery, which in turn provides power to your car’s electric, controlling the ignition, radio, air-conditioning, windows and lights. The power is generated by your car’s engine which is transferred to the alternator by turning an electromagnetic core. It then transfers an electric current through your wires and into your car’s battery and other electric components.  

How can you tell if your alternator needs replacing?  

If your alternator is faulty or needs replacing, you’ll notice the impact on the performance of your vehicle. However, these symptoms can often be confused with a faulty or dead battery. Some of the signs of a faulty car alternator include; 

  • Drained Battery: Your alternator is responsible for charging the battery while the engine is running,  meaning that if it stops working your battery will not be able to charge itself.  
  • Dimming or flickering lights: Your alternator is responsible for delivering power to your lights. If it’s not working properly, it will mean that your lights will have to rely on battery power alone to keep them running, which is less powerful than maintaining them with an alternator.  
  • Electrical faults: The alternator powers all the electrical components in your vehicle. If it fails, so will your electrical components such as windows, air-conditioning and radio.  
  • Battery warning light: Most cars will have a warning light to tell them there is an issue with the charging system.  
  • Stalling or trouble starting the engine: The alternator delivers power to your ignition and fuel injection system. If it fails, it can cause your engine to lose power which can lead to stalling or could even mean your car won’t start at all!  

How can Merityre help?

Here at Merityre, we offer peace of mind with any battery-related issues thanks to our free battery check service. Find your local Merityre Specialist where one of our trained vehicle experts will be happy to help.