Alternator Whining Noise: 5 Ways to Fix Bad Alternator Sound

A whining alternator is not uncommon, especially during the winter. There are several reasons responsible for such noise like Extra load, shaft bearings, a faulty diode, etc. Anyway, we will assist you in resolving your noisy alternator in this article further. And, you will undoubtedly be able to get rid of the alternator whining noise by yourself. Read on.

Why My Alternator Is Whining

The alternator is a core part of modern automobiles. Modern cars have an alternator, a particular kind of electric generator, to power the electrical system while the engine is running and charge the battery. 

Occasionally the alternator becomes overloaded by carrying an additional load of electrical accessories and errors, causing noises like grinding and whining.

There are several factors responsible for alternating whining noise. And the key causes we have identified are:

  1. Due to the magnetic forces involved in producing electricity, an alternator that is producing a lot of electricity makes a whining noise.
  2. The alternator’s defective diode can be the source of the whining noise.
  3. Worn shaft bearings may be the cause of an alternator that whines. There can be more sources of noise. We will talk about them later in our article.

How to Fix the Alternator Whining Noise

As we have already said, there are several responsible reasons for alternating whining noise. So, the solutions are also quite few in number. Eventually, you will get to know them one by one further.

1. Check the Worn-Out Bearings and Brushes and Replace Them

Together, bearings and brushes produce electricity. The alternator may begin to make a particular noise if these parts are worn out. For example, worn-out bearings often produce a whining sound.

Some common signs of worn-out bearings and brushes, in addition to the alternator whining noise, include:

  • Dim Lights
  • Low Charged Battery
  • Stuck Rotors
  • Slow Shifting

This is commonly the result of a low voltage output caused by bearings and brushes that are not functioning properly.

How to Check the Bearings

Use a rubber hose for this. It works in a manner akin to a stethoscope. Put one end of the hose against your ear, and the other on the metal alternator case. You may have a bearing failure that starts in the alternator if you hear loud grinding or squeaking while listening, in which case you will need to replace the bearing.

Steps to Replace the Bearings and Bushes

You must replace the bearings and bushes if they are worn out. Follow these steps to do that:

Step 1: Alternator Belt Removal 

Remove the belt from the alternator carefully.

Step 2: Detach the Alternator from The Engine

Use a socket wrench to remove the alternator’s bolt from the engine.

Step 3: Remove the Bushes and Bearings.

To remove the bearing, first remove half of the alternator, second the rotor, then remove the bearings.

Step 4: Replace the Bushes and Bearings.

You must pay close attention to this because a defective alternator won’t effectively charge your battery.

Step 5: Reinstall the Alternator with Bolts.

Now reassemble and install the alternator like before.

Step 6: Replace the Alternator Belt.

And finally, check the placement and install the belt.

2. Check the Diodes and Replace Them if Needed

The rectifier assembly, which converts the alternator’s current output to direct current, includes the alternator diodes as a part. 

How to Check the Diodes 

You can easily do it with a voltmeter. Just remember, any fraction in the voltmeter display indicates a faulty alternator diode.

  • Set the voltmeter to the lowest AC voltage scale setting.
  • Start the engine again and let it run for a while at 1200 rpm.
  • Connect the voltmeter probes.
  • Set the display to zero (0.00).
  • Check for any fraction in the display.

If you find any, then it needs a replacement ASAP.

Another Way to Check the Alternator Diode Is,

Connect the red wire of the multimeter to the generator’s red major terminal (positive terminal), and the other wire to the generator shell. If the resistance reading is greater than 550 ohms then the alternator diode is functioning properly.

NOTE: If one or two diodes have failed, then you can replace them easily. But if the count is more than that, then you have to replace your alternator. To replace the diodes, go to your nearest mechanic shop.

Other Most Common Causes of Noisy Alternators with Solutions

There are many components inside the alternator. Any worn or loosened component has the possibility to malfunction and create noise. Some common reasons for a noisy alternator are

1. Loose Alternator Belt.

Transferring power from the engine crankshaft to different components is the function of the alternator belt. You can experience performance troubles with your car if the belt is weakening or becoming loose. It might easily overheat.

HOW TO FIX IT: If the alternator belt is loose, the pulley needs to be tightened. To do this:

  • Find the alternator’s belt and pulley.
  • With a gauge for belt tension, tighten the pulley on the belt.

2. Loose Bolts.

If the bolt is loose, just tighten the bolts that hold the bracket and alternator together. An alternator typically has three bolts: one up front and two down back.

HOW TO FIX IT: Find the bolts first, then lightly tighten them with a socket wrench. Do not tighten too much.

3. Insufficient Bearing Fluid

The case can also happens from insufficient bearing fluid. It’s important to consider the fluid’s environment. The majority of fluid products include labels that list the kind, frequency of relubrication, and quantities; however, it’s essential never to combine different lubricant types.

HOW TO FIX IT: You can use any lithium-based lubricant to lube your bearings. Due to their ability to function well in both high and low temperatures and their water resistance, lithium-based greases are pretty popular as bearing grease.

4. Faulty Rotors

An alternator’s rotor is one of its parts and a part of its excitation system. However, the efficiency of an alternator is unaffected by a faulty rotor. But, the noise it makes can be problematic.

HOW TO FIX IT: Just remove the alternator, take the rotor out and replace it with a new one. Then reinstall it. But, make sure the rotor fits your alternator.

Indicators of An Weak Alternator

These warning signs may indicate a weak alternator:

  1. On the dashboard, your battery light is on.
  2. Your engine is starting to crank slowly or not at all.
  3. The headlights, batteries, and interior lights also feel insufficient.
  4. There are grinding or whining sounds coming from the alternator.
  5. You’ve tried to jump-start your car but were unable to do so.

How to Test an Alternator with A Multimeter

Alternator with A Multimeter

1st Phase:

You can test your alternator with a multimeter. Make sure the positive and negative terminals on your alternator are clean. and adjust the multimeter to DC Volts above 15.

  • Connect the red cable of the multimeter to the positive terminal and the black cable to the negative terminal.
  • An alternator reading of around 12.6 is optimal.
  • Once the engine is running, notice the reading between 14.2 and 14.7.

A reading of above 14.7 indicates an overcharge of the battery, whereas a reading of under 14.2 indicates an undercharge of the battery by the alternator.

2nd Phase:

  • Make sure the voltage reading doesn’t drop below 13 when turning on the lights, radio, fog lights, fan, and other accessories.
  • The reading should be higher than 12.6 before you turn the car off.

If any of these readings are incorrect, your alternator probably has a problem, and you should take it to a mechanic.

Learn more about how to test a car’s alternator.

Maintenance Tips to Keep an Alternator from Whining

Maintaining a regular maintenance schedule is one of the easiest solutions to fix a noisy alternator. Here are some maintenance suggestions to keep your alternator in good working order:

Clean the outer surface: Clean your alternator’s surface of any mud, dust, or grime. By doing this, you can protect it from overheating and delay the onset of wear and tear.

Verify all connections: Verify that every connection on the alternator is tight and corrosion-free. Most importantly, make sure that none of the cabling leading to your alternator is twisted or cracked.

Regularly check the alternator: At the very least once every year, check your alternator. Check for wear and tear on the belt, pulleys, and bearings. Do not hesitate to replace the component if you notice any damage.

Every five years, replace the belt: Your alternator may start making noise if your belt is worn out. It is preferable to replace a belt if it is older than five years. In the same way, if the belt exhibits any signs of loosening or tearing, replace it.

Every year, lubricate the bearings: Lubricating the bearings will keep them operating efficiently and stop them from producing noise. Must use a lithium-based lubricant.
If the voltage regulator is faulty, replace it: Your alternator may malfunction as a result of a bad voltage regulator, which can lead to other issues like a dead battery or poor lighting. Test the voltage regulator first to be sure that’s the issue, though, before you replace it.


Does a Bad Alternator Whine?

A bad car alternator that isn’t generating any electricity doesn’t make a whining sound. Instead of whining, it makes a squeaking, screeching, scraping, grinding, or no sound, depending on what fails. But the majority of the time there is silence.

What Makes the Alternator Whine?

There are filter capacitors in the alternator. If they fail, they make the alternator whine. The main cause of whining sounds is an extra load on the alternator. Another option is a bearing or a faulty diode, or occasionally the cold.

Can You Drive when Your Alternator Is Whining?

As long as your battery is charged, you can continue to drive with a faulty alternator bearing. However, there is a chance that your battery will die. You’ll require a repair right away because the alternator is an essential component of the battery’s power system.

How Much Does an Alternator Replacement Cost?

You can spend $100 to $200 on a new part if you are purchasing aftermarket components. Otherwise, a new alternator should cost between $200 and $350 if you use OEM parts. Depending on the mechanic’s hourly rate, labor charges will be closer to $200.

Do Alternators Fail Suddenly?

Alternators can break down quickly or gradually over time. There are certain indications you may watch out for if your alternator is gradually losing efficiency over time. such as dim headlights, dead batteries, slow-functioning accessories, and so on.

Final Words!

I hope you now know why your alternator is making a whining noise and how to fix it.

However, if your alternator is continually giving you trouble, fixing the alternator’s whining noise may not be sufficient. It might be time to replace it with a better model.

But make sure you read your car’s manual so you can follow the exact steps and install the right parts. If the issue continues, go to a professional mechanic.

Robert Faulkner
Robert Faulkner

I'm Robert Faulkner, My profession is soundproofing. I'm still acquiring knowledge about sound and soundproofing procedures. Furthermore, I am very good at noise management and like sharing soundproofing ideas and methods for any situation.

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