The alternator generates electricity to fire the spark plugs, power the computer, and run all the electrical components such as the lights, stereo, electric windows etc., plus recharge the battery after you start the vehicle
In general they are very reliable, and trouble free, however, they can have issues and may on occasion need repair or replacement.
Common problems with alternators
Often the first time you'll discover your alternator is faulty is when the battery goes dead (there can be several causes of this, not just alternator failure), or when the battery warning light appears the dashboard.
On modern cars, the ECU monitors the alternator output and if it drops too low, the battery warning light will come on. When this happens, it could be caused by the alternator simply being worn out – the brushes which transmit the electricity to the rotor wear down over time - or it could be an issue with the voltage regulator, or 'smart charge' set up in the ECU, or is could be as simple as an internal short or break.
With older alternators repair is straightforward: With the component removed an auto-electrician can test it, diagnose and rectify any issues, and install a new alternator if needed. Alternators on newer, more computerized cars, may appear to be more sophisticated, but the alternator works the same way. The biggest difference is that the voltage regulation is now integral to the computer that runs the car.
Testing the voltage output of the alternator at a given RPM is the primary method of diagnosing an issue with it, not matter what car it is off of.
The alternator can also appear to fail if the serpentine drive belt snaps, or is very loose. You're also likely to suffer from engine overheating, and power steering loss, at the same time, so in the event of a snapped belt, it's usually apparent immediately what happened.
How to extend the life of your alternator
There's not a great deal you can do to extend the life of the alternator, and failure is frequently sudden, rather than gradual – so you could have a perfectly functional alternator one day, and a dead one the next.
If you notice your headlights flickering at a stop light, that could be warning sign, as can a battery warning light that flickers, or stays on longer than usual when you first start the car.
Keeping the engine compartment clean and free from dirt and debris is wise, and ensure that the serpentine belt and tensioner is replaced as per the servicing schedule, and you should get many years of service from your alternator.
How long should an alternator last?
Alternators are generally trouble free – they can often last for the life of the car, and issues are especially rare on vehicles under 5 years old. Even though they're an incredibly hard-working component, it's not uncommon for them to reach 100,000 miles.
You're more likely to have an issue with the electrical side of things, as the mechanics of an alternator are very straightforward, with very few moving parts. However, it only takes a minor mishap with any aftermarket accessory install to cause a multitude of electrical problems.
How much does it cost to replace an alternator yourself?
The actual alternator can cost from $50-$300 depending on the application, and installing it can be as simple as removing a couple of bolts, or complicated enough to take all day, depending on how deep it's buried in the engine bay!
All you need is a basic tool kit, and socket set in most cases – oh and use this as an opportunity to replace the serpentine belt at the same time. Our new Haynes OnDemand service will show you how to replace your car's alternator, as well as replace your serpentine belt!