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Car Parts Basics: The Alternator | The Allstate Blog

Car Parts Basics: the Alternator

Your car's alternator is an important part of its mechanical operation, but do you know what it does and how it might fail? Auto maintenance and repair specialist The Humble Mechanic explains the role your alternator plays and some common ways it may break down. https://youtu.be/gNC2DmMtZ4o Watch more videos by The Humble Mechanic. Follow him on… Allstate https://i0.wp.com/blog.allstate.com/wp-content/uploads/2018/02/Alternator-image.png?fit=684%2C365&ssl=1
a car's alternator

Your car’s alternator is an important part of its mechanical operation, but do you know what it does and how it might fail? Auto maintenance and repair specialist The Humble Mechanic explains the role your alternator plays and some common ways it may break down.

Watch more videos by The Humble Mechanic. Follow him on his blogTwitter and Facebook.


Hey everybody, it’s Charles from HumbleMechanic.com and today we are talking alternators.

The alternator is one of those car parts that most people have heard of, but maybe they don’t know where it is, what exactly it does how it works and, most importantly, how it fails. Most alternators are located towards the front of the engine. They’re mounted on an accessory bracket and driven by either a serpentine belt or their own accessory belt.

The alternator has the very simple task of providing electrical power to our entire vehicle. In addition to that, it’s responsible for keeping our battery properly charged while the vehicles running. It does this by converting mechanical energy – the rotation of our engine – into electrical energy in the form of AC power.

It all starts by the serpentine belt rotating the pulley of the alternator. This pulley is attached to the rotor inside the alternator housing. This rotor spins inside what’s called the stator – the rotating magnetic field of the rotor, induces electricity into the stator and this is what produces our AC or alternating current power.

Now, before the vehicle can use this AC power, it actually needs to be converted into DC. This is done by a component called a bridge rectifier. The bridge rectifier is simply a series of diodes or one-way electrical check valves that converts that from AC into DC.

When it comes to output, the normal output is anywhere from 13 to about 14 and a half volts on most alternators. This is regulated by an internal component called a voltage regulator inside the alternator. Some vehicles may have a separate computer that regulates this output voltage.

When it comes to failures, there’s any number of ways an alternator can fail. An internal failure of the alternator, of course, is the most common thing and does cover a wide variety of components. Typically, when this happens you’ll get a warning light on in your dash. This warning light is most often shaped like a vehicle battery. It is important to note that your vehicle does a self-test of the system when you first turn your key on, so the battery light almost always comes on then. But, if that light doesn’t turn off when you start your car, or comes on while you’re driving, you may have an issue with the alternator.

In many vehicles accessories can also stop working. Modern cars are very smart and can start to deactivate systems that are not vital to car operation. Things like air-conditioning and four-wheel drive can typically be shut off first. You’ll most often get that battery light in addition to some other warnings, saying the vehicle is shutting systems down.

The one that most folks are familiar with is a dead battery, and this may very well be an alternator issue, or it might be simply a bad or worn-out battery.

If your car is slow to start or won’t start at all, this could be a sign of an alternator not charging your vehicle’s battery. But, it’s important to note that there are plenty of other things that can cause that symptom. A common sign of a failing – not completely bad – alternator is going to be dim light output. Maybe headlights are dim, perhaps dash lights or interior lights aren’t lighting up as bright as they should.

In addition to those failures, an issue with the serpentine belt, the alternator pulley or accessory belt can also cause low or no charging voltage. When it comes to cost of replacement, it can widely vary. Anywhere from a couple hundred bucks into the thousands of dollars. If you’re considering a DIY, many alternators are actually really easy to replace. However, it’s important to note that some do require extensive measures in order just to access the alternator.

Alright guys, there you have it – a basic understanding of the vehicle’s alternator if you have any questions or comments, feel free to leave them below. If you want to check out more of my videos, head over to HumbleMechanic.com.

Thank you guys so much for watching, and I will see you next time.

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