Driver's Guide

What Can Damage an Alternator?

What can damage an alternator? An alternator can be damaged by several factors including overloading, worn-out bearings, slipping belts, corrosion, and exposure to heat. You want to avoid these issues and extend the life of the alternator by regularly maintaining the system and addressing any issues promptly, either by yourself or with professional assistance.

What can damage an alternator?

What can damage an alternator

Below is what would make an alternator go bad:

  1. Dead or dying battery

Oftentimes, you can have a damaged alternator if it is being stressed by a dead or dying battery. The normal duty cycle of an alternator will charge a car’s battery while the car is running.

Accessories like an air conditioner or lighting system won’t give the alternator a chance to rest.

Charging at full power for days or even weeks can quickly wear out an alternator. This is because the unit is trying to charge a battery that acts more like a huge load than a store of energy, which shortens the alternator’s life.

  1. Loose battery terminals

If the alternator is damaged, it could be because the battery terminals are loose or rusty from acid buildup. In this case, the alternator will either not start charging at all or will bounce from low to high voltage erratically. This will also result in the regulator failing.

In this situation, simply check that the battery cables are securely connected and corrosion-free.

  1. A broken belt or a broken pulley

Alternators generate electrical energy for cars by using the mechanical power of a belt and pulley.  The alternator belt and pulleys are not very durable, which means they can easily break.

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Pulleys typically last for a long time before becoming damaged due to age. Belts are flimsier and, given enough time, will begin to crack and even break. If either of these things occurred, no mechanical energy would be generated for the alternator to convert.

  1. Alternator has been overworked

If the alternator loses its power over time, it won’t be able to keep the electrical system running as it should.

Check the alternator’s performance by measuring the voltage at the battery terminals to be able to tell if it can handle all of the power that you’re requesting. If the battery voltage falls below 12 volts, it’s time to upgrade to a more powerful alternator!

Wrong capacity alternators will wear out quickly and cause you problems.

  1. Reversing the polarity of the jumper cable

Is it possible to damage an alternator by jump starting a car? Well, only if done incorrectly! This is common in jumping vehicles because the alternator is already turned on.

If you jump the car and switch the polarity of the jumper cables, the computer-controlled regulator and diodes will be damaged almost immediately. Also, the process of connecting and disconnecting the cars can cause current surges that can damage the alternator of either car.

  1. Reversing the polarity when installing a new battery

If you installed your new battery incorrectly, you should notice a frightening spark, and your car will die. Fixing something like this is not a do-it-yourself project, and it is extremely complicated due to the numerous issues you have just created. Simply take your car to a repair shop.

Cranking the engine again (in this state) can cause it to turn in the opposite direction! The damage begins the moment the reverse battery connection is made. Many fuses have already blown, and any unprotected vehicle components have been destroyed.

When the battery is connected backward, the rectifying diodes on the alternator immediately blow. This causes the alternator to overheat and fail.

  1. Contamination from dust and dirt

One of the most important things you can do to keep the alternator in good working order is to keep it clean and dry. When dust, dirt, and other particles get into the alternator, it can cause the brushes and shorts to wear out over time.

Dirt can also be a factor in bearing failure. You should keep a car’s alternator clean and free of dirt to ensure long service life.

  1. Oil leaks

Oil leaks can also damage an alternator, so get them repaired as soon as possible. It’s impossible to predict how much oil will be required to cause the alternator to fail. On the other hand, oil leaking from valve cover gaskets can be what can damage an alternator.

If the alternator is leaking oil, you should replace it along with the valve cover gasket.

  1. Malfunctioning fuse

Cars use fuses to keep the alternator functional. These fuses fail over time or when there is a power surge. In this scenario, you can have a damaged alternator.

If your alternator isn’t working right, look in your owner’s manual to find out where the fuse for the alternator is and if it’s blown.

  1. Shorted alternator (insulation failure)

If insulation fails in any part of the alternator, it could create a short. A melted wire shorting to ground or an overcapacity fuse could be what can damage an alternator.

When a fuse continues to blow after being replaced, this is an indication of a short. In addition, if your ECM just blew out, this is a good indication of an alternator short.

So, instead of going through batteries, look for an alternator short. This could be your issue if you are changing one battery after another.


Alternators can stop working without warning for reasons other than age, like damage from bad wiring or a bad battery.

Overloading the alternator’s components is another common cause of what can damage an alternator. Overloading occurs when the system attempts to draw more current from the alternator than it was designed for, resulting in overheating, blown fuses, and faulty rectifier diodes.

A loose serpentine belt, which is another name for an alternator belt, can cause charging problems but usually won’t hurt the alternator. To avoid damage to your alternator, simply keep your alternator belt in good condition and your wiring and connections in good working order.

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Bernard Juchli

Bernard Juchli is an experienced racer, mechanic and team owner who trusts Avon Tyres.Bernard is the lead driver and force behind his Big Dog Garage Race Team. He is the General Manager and Chief Mechanic of Jay Leno’s Garage. Bernard and his crew of seven are responsible for all repairs, restoration and fabrication of Jay’s incredible automobile and motorcycle collection.

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