Alternator Making Noise: Common Causes and Repair

The alternator is a crucial car component that generates power to run the engine and charge the battery. If the alternator is making noise, it could signify a serious problem. Therefore, it’s essential to determine what causes an alternator to make noise and how you can fix it.

If your alternator makes noises, it could be due to worn bearings and bushes, a loose belt, loose bolts, low bearing fluid, or a damaged rotor. To fix it, replace the worn or damaged components, tighten the loose belt and bolts, and add more lubricant to the bearings.

In this article, I’ll discuss each of these potential causes in more detail and how to fix them. Read on for more information on these and insights into what a bad alternator may sound like.

What Does a Bad Alternator Sound Like?

A bad alternator will make a high-pitched whining noise. It may also make a grinding noise, and you might hear it knocking or squeaking. If you’re not sure whether your alternator is bad, it’s best to get it looked at by a professional.

Another sure-fire way to determine whether the alternator is bad is to test it with a voltmeter, which gives an accurate reading of the voltage output from the alternator.

If you don’t already own a voltmeter, I highly recommend getting the AstroAI 2000 Counts Digital Multimeter. It’s easy to use, versatile, and offers incredible accuracy.

To test your alternator using a voltmeter, follow these steps:

  1. Ensure the engine is turned off and the car is in park
  2. Connect the voltmeter to the battery terminals
  3. Turn on the voltmeter and check the reading. You should get a reading of between 13.9 and 14.8 volts
  4. If the reading is below 12 volts, then the alternator is not working correctly and needs to be fixed or replaced

Here are some additional tell-tale signs of a failing alternator:

  • The battery dies quickly: Your battery needs the alternator to recharge it when it’s running low on power. If the battery is dying quickly, it could be because the alternator can’t keep up with its demands.
  • The check engine light is on: The check engine light activates when there’s an issue with the engine. If the light is on and you suspect it’s because of the alternator, take it in for a diagnostic test.
  • The car won’t start: If the alternator is failing, it won’t be able to provide enough power to start the engine.
  • The headlights are dim: The alternator also provides power for the headlights. If they’re dim, it could signify that the alternator is not working properly.
  • The car stalls: A failing alternator can’t provide enough power to run all the electrical components in the car, meaning the vehicle will stall.

Key Takeaway: An alternator is responsible for generating power to run all the electrical components in your car. Therefore, if it’s not working correctly, you’ll likely experience one or more of the symptoms mentioned above.

Keep in mind that an alternator can also fail without making any noise at all – so if you’re experiencing any of the symptoms listed above, it’s best to have your car checked out by a mechanic.

Common Causes of an Alternator Making Noise

Your alternator usually makes noise because one or more of its components is loose or worn out. For example, worn-out bearings and bushes, loose belts, and a damaged rotor can cause an alternator to make noise. Moreover, an alternator can also make noise due to insufficient lubrication.

Here’s a rundown of the most common causes of an alternator making noise and their signs:

Worn Out Bearings and Brushes

Bearings are metal discs that fit between the rotor and stator. They help the rotor spin, while also keeping the stator in place. On the other hand, brushes are small pieces of carbon that contact the commutator (a rotating switch that conducts electricity).

Together, bearings and brushes generate electricity. If either of these components is worn out, the alternator may start making a distinct noise. For example, worn-out bearings may cause a high-pitched whining sound.

Similarly, worn-out bushes tend to cause a grinding noise. This occurs due to the misalignment of the rotor shaft as the bushes become loose.

Besides the alternator making noise, the most common signs of worn-out bearings and brushes include:

  • Dim lights: This is usually due to a lack of electricity caused by the bearings and brushes not working correctly.
  • Slow cranking: This may be due to a low voltage output.
  • An empty battery: In some cases, an empty battery may be caused by the fact that the alternator isn’t charging it properly.
  • A seized rotor: The rotor may seize if the bearings and brushes are worn-out.

Note: Lack of lubricant is the most common cause of bearings and brushes wearing out. When the bearings and brushes aren’t properly lubricated, they overheat and wear out prematurely.

Alternator Belt Is Loose or Worn Out

The alternator belt is responsible for transferring power from the engine to the alternator. If it’s loose or worn out, it may contact other engine components and cause them to vibrate. This can cause the alternator to start producing noise.

The most common signs of a loose or worn-out alternator belt are:

  • A screeching noise: If the alternator belt is loose, it may make a screeching sound when the car first starts.
  • A squealing noise: A worn-out alternator belt may also squeal, especially when the car starts or accelerates.
  • A grinding noise: If the alternator belt is excessively worn, it may start to grind against other engine parts.

Note: The most common cause of an alternator belt becoming loose or worn out is lack of maintenance. For example, if the belt isn’t replaced when it’s due, it will eventually stretch and become loose.

Bolts Are Loose

Alternators come with bolts that secure them to the engine. As you drive, the engine’s vibrations may cause these bolts to loosen. Once they’re loose, they can cause the alternator to make noise.

The most common signs of loose bolts are:

  • A rattling noise: The alternator may rattle if its bolts become too loose. This is due to the engine’s vibration causing the alternator to move around.
  • A grinding noise: If the alternator is rubbing against other engine parts, it may make a grinding noise.

Note: Lack of maintenance is the most common cause of loose bolts. For example, if the bolts aren’t tightened when the alternator is replaced, they may become loose over time.

Alternator Bearings Are Low on Fluid

Alternator bearings need special lubricant or grease to keep them cool and lubricated. If they’re not lubricated enough, the bearings may start to make noise due to friction.

The most common signs of low fluid level in the alternator bearings are:

  • A squealing noise: The alternator may squeal if it’s low on fluid. Besides, lack of lubrication may cause the bearings to overheat, wearing them out faster.
  • A grinding noise: The alternator may also make a grinding noise if it’s low on fluid. This is due to the bearings not being adequately lubricated.

Note: The most common cause of an alternator being low on fluid is leaking seals. When the seals leak, the fluid level decreases, and the alternator may overheat.

Rotor Is Damaged

The rotor is a part of the alternator that spins and creates electricity. If the rotor is damaged, its shaft may misalign, causing noise as it rubs against other alternator parts.

The most common signs of a damaged rotor are:

  • A squealing noise: A damaged rotor may squeal as it spins. This is due to its rubbing against other parts of the alternator.
  • A grinding noise: A damaged rotor may also make a grinding noise as it spins. This is due to the shaft of the rotor being misaligned.

How Long Can a Noisy Alternator Last?

A noisy alternator can last a maximum of 30 minutes. After that, it’ll either need to be repaired or replaced. Otherwise, it may end up damaging other car components.

If you’re experiencing problems regarding your alternator, it’s best to take it in for repairs as quickly as possible. A certified mechanic can diagnose the problem and let you know whether it’s fixable or not.

Otherwise, you risk facing several consequences, including the following:

  • The alternator may catch a fire: A damaged or faulty alternator may overheat and start a fire.
  • Reduced battery life: If the alternator isn’t working correctly, it won’t charge the battery fully, shortening your battery’s life.
  • Damage to other engine parts: A faulty alternator can also damage other car components, including the starter and the voltage regulator.
  • The radio may turn off or cut out: A failing alternator may not provide enough power to the car’s electrical system, resulting in the radio turning off or cutting out.
  • Steering becomes difficult: If your car utilizes power steering, a failing alternator may make it difficult to steer.

These consequences can be expensive to fix and may even put your safety at risk. For these reasons, it’s essential to have your alternator checked regularly and to have it repaired or replaced as quickly as possible if it’s not working correctly.

How to Fix a Noisy Alternator

You can fix a noisy alternator by replacing the bearings and bushes, tightening the alternator belt, tightening the bolts, lubricating the bearings, replacing the rotor, replacing the alternator seals, carrying out a strict maintenance schedule, or calling in a professional mechanic for help.

Here’s a rundown of the steps to follow in each case:

1. Replace the Bearings and Bushes

If the bearings and bushes are worn out, you’ll need to replace them. To do that, follow these steps:

  1. Remove the alternator belt.
  2. Unbolt the alternator from the engine using a socket wrench.
  3. Remove the bearings and bushes.
  4. Install new bearings and bushes.
  5. Bolt the alternator back into place.
  6. Reinstall the alternator belt.

Here’s a tutorial on how to replace noisy alternator bearings:

2. Tighten the Alternator Belt

If the alternator belt is loose, you’ll need to tighten its pulley. To do so, follow these steps:

  1. Park your car and shut off the engine.
  2. Open the hood.
  3. Find the alternator belt and its pulley.
  4. Using a belt tension gauge, tighten the belt’s pulley. If you don’t have a belt tension gauge, use your socket wrench to tighten the bolts.

The following video demonstrates how to tighten an alternator belt:

3. Tighten the Bolts

If the alternator bolts are loose, you’ll need to tighten them. To do so, follow these steps:

  1. Park your car and shut off the engine.
  2. Open the hood.
  3. Find the alternator and its bolts.
  4. Using your socket wrench, tighten the bolts.

Caution: Make sure to not over tighten the bolts by reading your car’s manual before attempting to fix them.

4. Lubricate the Bearings

If the bearings are dry, you’ll need to lubricate them. To do so, follow these steps:

  1. Park your car and shut off the engine.
  2. Open the hood.
  3. Find the alternator and its bearings.
  4. Using a bearing grease gun, apply grease to the bearings.

Note: If the bearings are worn-out, replace instead of lubricating them.

5. Replace the Rotor

If the rotor is damaged, you’ll need to replace it. Hera’s how you can do it:

  1. Remove the alternator belt.
  2. Unbolt the alternator from the engine using a socket wrench.
  3. Remove the damaged rotor.
  4. Install a new rotor.
  5. Bolt the alternator back into place.
  6. Reinstall the alternator belt.

Tip: Before installing the new rotor, inspect it and ensure it’s compatible with the alternator.

6. Replace the Alternator Seals

If the alternator seals are leaking, you’ll need to replace them. To do so, follow these steps:

  1. Remove the alternator belt.
  2. Unbolt the alternator from the engine using a socket wrench.
  3. Remove the old seals.
  4. Install new seals.
  5. Bolt the alternator back into place.
  6. Reinstall the alternator belt.

Caveat: Before installing new components on your alternator, it’s essential to consult your car’s owner’s manual. Each make and model has a specific alternator replacement procedure that you should follow to ensure that the alternator is installed correctly and able to function.

7. Carry Out a Strict Maintenance Schedule

One of the best ways to fix a noisy alternator is to carry out a strict maintenance schedule. This means regularly checking the components and replacing faulty ones as soon as you spot them. Doing so will help you catch any potential problems early on and prevent them from getting worse.

Here are a few maintenance tips to keep your alternator running smoothly:

  • Inspect the alternator regularly: Although there’s no set schedule for this, it’s good to inspect your alternator at least once a year. Ensure you check the belt, pulleys, and bearings for wear and tear. If you spot any damage, don’t hesitate to replace the component.
  • Replace the belt if it’s worn-out (or every seven years): A worn-out belt can cause your alternator to make noise. If the belt is more than six years old, it’s best to replace it. Likewise, if the belt shows any signs of cracking or fraying, it’s time for a replacement.
  • Lubricate the bearings every year: This will help keep them running smoothly and prevent them from making noise.
  • Replace the voltage regulator if it’s faulty: A faulty voltage regulator can cause your alternator to malfunction, causing other problems like an empty battery or dim lights. However, before replacing the voltage regulator, it’s crucial to test it to make sure that’s the problem. You can do so using a voltmeter.
  • Check the connections: Make sure all of the alternator’s connections are secure and free of corrosion. Most notably, ensure all the wiring to your alternator is in good condition and free of fraying or damage.
  • Clean the exterior: Remove any dirt, debris, or grime from the surface of your alternator. This will help keep it running cooler and prevent premature wear and tear.
  • Upgrade to a higher quality alternator: If you’re constantly having problems surrounding your alternator, it might be time to upgrade to a higher quality one.

8. Call a Professional Mechanic for Help

If your alternator is still making noise after you’ve tried all of the above tips, it’s best to call a professional mechanic for help. They’ll help diagnose the problem and fix it quickly and efficiently.

Here are some tips on choosing the best mechanic for the job:

  • Look for a mechanic who’s certified: A certified mechanic will have the necessary training and expertise to diagnose and fix your alternator.
  • Check the mechanic’s reviews: Read online reviews from past customers to get an idea of the quality of service they provide.
  • Get a quote before you book: This will help you know how much the repair will cost beforehand.
  • Ask around for recommendations: Talk to friends and family members who have hired a mechanic in the past and see if they can recommend someone.
  • Take your car to a dealership: If all else fails, take your car to a dealership. They’ll have certified mechanics on staff who can help.

Final Thoughts

If your alternator is making noise, it could be due to several reasons, including worn-out bearings or bushes, a loose alternator belt, a damaged rotor or stator, or low fluid levels. In most cases, you can solve the problem by carrying out a strict maintenance schedule and replacing any faulty components.

However, ensure you read your car’s manual so that you go through the correct procedure and install the right components. If the problem persists, call in a professional mechanic to help.




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