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Maybe you’re fairly familiar with cars. You know what your engine is, how to check your oil, what to do when you have a flat tire. But what if a mechanic tells you that your alternator needs to be replaced? What exactly is an alternator, and what kind of maintenance does it require?

Your car’s alternator is a critical part of its power supply system, which works to recharge the car’s battery while the engine is running. If your alternator fails, your car’s battery will quickly drain and then die, and its electronic components will malfunction. An alternator does not require routine maintenance, it simply must be replaced if it fails.

Read on to learn some more information about how your alternator functions, and when you can expect to have to replace it.

How long does an alternator last?

Alternators are typically very long-lasting, and only need to be replaced when they stop working. It depends on the sort of car and the alternator it contains, but typically alternators last for at least 100,000–150,000 miles in a car that is driven regularly. Often, they will last longer than this, even for the whole life of your vehicle.

Like many things in your car, routine (daily) driving is good for your alternator. A car that sits for long periods of time without being driven will often see its alternator fail at a lower mileage. Exposure to extreme heat or to excessive water can also impact the longevity of your alternator.

What all does an alternator do?

Because it is a key component of the car’s power system, the alternator impacts many parts of your car’s functioning.

When you turn the key and start your car, it is the battery which provides the power to start the engine. However, once the car is running, the alternator takes over, providing power to the electronic components of your car such as your lights and headlights, radio and dashboard instruments, electric steering, and more. While you drive, the alternator also continues to charge your car battery by converting the mechanical energy of your running engine into electricity.

It is for this reason that your car battery can die if you let your car idle for too long with the engine running without driving, or if you let your car sit off for days at a time without driving it.

When does my alternator need replaced?

If your alternator fails, it will need to be replaced immediately in order to keep your car functioning. If you see any of the tell-tale signs of a failing alternator such as a repeatedly dead battery, variances in the brightness of your headlights, a slow-starting or stalling engine, unusual smells or noises coming from your car, a check battery light, or failing electrical components such as power windows or radio, it is a good idea to reach out to a mechanic immediately and to get them to come diagnose the problem.