To know what the heck an alternator IS, we must first explore what the heck an alternator IS NOT. An alternator is not: 

  1. A new invention that changes people’s minds to a different way of thinking
  2. A Green Party political activist who has run for President of the United States multiple times
  3. The name I gave my pet fish when I was in first grade
  4. A machine that creates the table in a Christian church at which the bread and wine are consecrated in communion services


So…what the heck is it then? 

The alternator charges the battery to power the electrical components in a vehicle. It uses battery power to create and send back more electricity.

They usually aren’t this squeaky clean.

How Does It Work?

Basically, the battery gives the alternator a little nudge, and the alternator does a roundhouse back onto the battery.

The first two science-y things to know are:

  1. If you move a magnet along a wire, it will create an electrical current.
  2. If you put an electrical current through a wire, it will create a magnetic field around the wire.

There are, of course, multiple parts to an alternator:

  • Rotor
    • The rotor consists of a coiled wire surrounded by magnets. The magnets’ poles are situated so that they are alternating.
    • It is driven by the crankshaft, which makes it rotate inside the stator.
    • The rotor receives power from the battery through metal brushes in the back of the alternator housing that contact slip rings, which are metal rings that fit around part of the rotor.
    • The rotation of the alternating magnets’ poles and the current in the wire from the battery through the stator creates an electromagnetic field with an alternating current.

  • Stator
    • The stator consists of wires wound in specific ways (windings) to conduct electricity created by the rotor’s electromagnetic field.
    • Those wires go into diodes, which turn the alternating current from the rotor’s electromagnetic field into a direct current that runs back to the battery.

  • Voltage Regulator
    • The voltage regulator is located in the back of the alternator housing. Attached to it are the metal brushes that contact the slip rings on the rotor.
    • This little device does just what it indicates in its name—it regulates the voltage of the electricity that the alternator puts out.
Common Problems

For many alternator problems, the best solution is to replace the whole thing with a new or rebuilt one because the parts can be expensive with more labor in addition to them. Here are some common problems with alternators:

  • Loose or worn rotor bearings
  • Worn belt (from crankshaft to alternator rotor)
  • Overheated or worn diodes
  • A bad battery can put extra stress on an alternator, causing it to over-work
  • Voltage regulator failure
Warning Signs

There are a few things you can listen or look for when it comes to detecting alternator failure. If you hear a squealing or grinding sound, it could be bad bearings. Did your battery indicator dash light come on? It could either mean a bad battery or trouble with the alternator. If your headlights and interior lights are dimmer or the battery indicator dash light only turns on when you’re using more electronic features (seat warmers, CD player, travel espresso machine, portable washer and dryer, etc.), that could point to a failing alternator.

Handpresso Coffee Machine for Automobiles is an actual thing. How have I not heard of this before?!?

So, there you have it. Now you know what the heck an alternator is NOT, what it IS, how it works, and learned that travel espresso machines ACTUALLY EXIST.


Tell me what other automotive parts baffle you. I’ll tell you what the heck they are!

Written by Ben Scharff

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