What does an alternator do?
Peter Sitkowski | 12th Sep 2024 | 6 minutes to read
The alternator is one of those critical yet often overlooked components of a vehicle that plays a pivotal role in its operation. For most, it’s a term heard occasionally at the mechanic’s shop or mentioned when the battery seems to be failing. However, understanding what an alternator does, its importance, and how it functions can help in recognising issues before they lead to bigger problems on the road.
We've broken down some of main things your alternator looks after and how to spot some of the issues that alternators can run into:
What is an Alternator?
An alternator is a key part of a car's electrical system. While the battery stores the electrical energy needed to start the engine, the alternator is responsible for generating electricity to keep the battery charged and to power all the electrical components of the vehicle while the engine is running. Think of it as the heart of the electrical system, continuously pumping energy to where it’s needed.
How an Alternator Works
The alternator works through a process known as electromagnetic induction. Inside the alternator, a rotor (which is a magnetic field) spins inside a set of windings (the stator). As the rotor spins, it generates a flow of electricity within the stator. This electricity is then converted from alternating current (AC) to direct current (DC) by a device called a rectifier, which allows it to be used by the car’s electrical system.
Why the Alternator is Crucial
The alternator powers all the electrical components of the car, including the headlights, dashboard lights, radio, power windows, air conditioning, and more. Without it, the battery would quickly drain, leaving the vehicle unable to function. While the battery is responsible for starting the car, it’s the alternator that keeps everything running once the engine is on.
A well-functioning alternator also ensures that the battery remains charged. If the alternator fails, the battery will eventually lose its charge because it’s not being replenished. This is why a failing alternator is often mistaken for a dead battery, as the symptoms can be very similar—dim lights, electrical malfunctions, and eventually, a vehicle that won’t start.
Signs of a Failing Alternator
It’s important to know the early symptoms of alternator failure as well as minor issues that can turn into larger problems.
Warning Lights on the Dashboard
One of the first signs that an alternator may be failing is the appearance of a warning light on the dashboard. This light is usually shaped like a battery but may also appear as “ALT” or “GEN.” It indicates that the voltage being produced by the alternator is below the required level, which could mean the alternator is starting to wear out.
Dimming or Flickering Lights
If you notice that your headlights are dimming or flickering, particularly when idling, it could be a sign that the alternator is struggling to keep up with the electrical demand. This issue might become more apparent when using multiple electrical components at once, such as the headlights, radio, and air conditioning.
Electrical Failures
A failing alternator can cause various electrical components to act up. You might experience problems with the power windows, dashboard lights, or even the radio. In some cases, the car might have trouble starting, or you might hear unusual sounds like a whining or grinding noise, which could indicate that the alternator’s bearings are wearing out.
Dead Battery
While a dead battery is often blamed on the battery itself, a faulty alternator can be the underlying cause. If the alternator isn’t charging the battery properly, the battery will eventually lose its charge, leading to a no-start situation. If you’ve recently replaced the battery and it dies again, the alternator might be the culprit.
The Process of Replacing an Alternator
Before replacing an alternator, it’s essential to ensure that it’s the root cause of the problem. A mechanic can perform tests to measure the voltage output of the alternator. If it’s below the recommended level, replacement is likely necessary.
When replacing an alternator, it’s important to choose one that matches the specifications of your vehicle. Alternators vary in terms of power output, and using one that’s too weak or too powerful can lead to further electrical issues. It’s advisable to consult with a professional or refer to the vehicle’s manual when selecting a replacement.
Professional Installation
While some car enthusiasts might attempt to replace an alternator themselves, it’s generally recommended to have it done by a professional. The alternator is connected to several critical components, and incorrect installation can lead to more serious problems. A professional mechanic will ensure that the new alternator is installed correctly and that it’s functioning properly before you hit the road.
Alternator Overview
The alternator is an essential component that ensures the proper functioning of a vehicle’s electrical system. By understanding its role, recognising the signs of potential failure, and taking proactive steps to maintain it, you can help ensure that your vehicle remains reliable and roadworthy. Whether you’re dealing with dim lights, a dead battery, or strange noises, paying attention to your alternator could save you from unexpected breakdowns and costly repairs.
