Why Do Alternators Go Bad?

Most alternators go bad because of worn bearings, which means the alternator is no longer able to spin as fast as it needs to.

A bad diode can also cause problems with your alternator, since a diode is what allows your alternator to regulate its voltage output.

Your belt can become loose or worn out, which will prevent your alternator from spinning properly and causing damage to either itself or other parts of your car.

And finally, if there’s a loss of connection between the alternator and battery, then you won’t be able to charge up your battery at all—and without a charged battery, there’s no power for anything else in the car!

Worn out bearings

When the bearings in an alternator begin to wear out, it can cause the alternator to fail. Bearings are used in an alternator for several reasons:

  • To support the rotor shaft
  • To help keep it cool by allowing air flow around it
  • To minimize vibration and noise caused by turning at high speeds

To check for worn bearings, look at your alternator’s pulley or fan. If there is any play between these items, then they need to be replaced as soon as possible.

If not addressed immediately you may find yourself stranded with a dead battery when you least expect it!

Bad diodes

The diode is a simple and reliable electrical component that allows current to flow in one direction but not the other. If a diode fails and electricity flows backwards, it can cause damage to your alternator.

Fortunately, diodes are easy to test for with an ohmmeter, and replacement is a fairly straightforward process if you have some basic tools on hand.

If you have access to testing equipment (a multimeter), check for continuity between each pair of leads at both ends of the diode.

If no continuity exists, then we can assume that this particular device has failed and should be replaced immediately before further damage occurs!

Loss of connection

If you suspect your alternator may have lost connection to the battery, first check that all of its connections are secure.

Check both ends of the wire to make sure it’s properly seated and not loose. You should also check that any other components connected to your alternator are securely attached.

Finally, check the connection between your car’s positive terminal and battery by using an ohm meter or voltmeter on its negative side. If there is no reading, this could be another sign of a problem with your alternator.

Loose or worn belt

A belt can become loose or worn and slip off the pulley. Another possibility is that it breaks, in which case you need to replace the belt with a new one.

If your alternator is working properly but your battery is draining too quickly, this may be due to an issue with the belt on your vehicle’s alternator.

If your vehicle has a serpentine belt that connects all of its accessory components together, it’s possible that its tensioner isn’t working correctly and needs adjustment. This could cause problems for other parts of your engine if left unchecked.

If there’s too much tension on one part of the serpentine belt, then other components like power steering pumps may not operate properly—and eventually could break down from overuse—or even worse: if too little tension exists on another part of the system, then those parts won’t be able to do their job efficiently either!


Alternators go bad for a variety of reasons, but the most common is because the bearings have worn out.

Alternators also go bad when diodes in the alternator burn out, which is why it’s important to replace them regularly. Alternators can also lose connection to the battery or belt, which can cause them to overheat and break down.

Alternators are very reliable, but they do have a limited lifespan. If you’re having trouble with your alternator, it’s likely because the alternator is getting old and needs to be replaced.

Alternators are made of electrical components, so as time goes on, those components will wear out and need to be replaced.

Steven Hatman
Steven Hatman

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