Alternator Noise: A Guide to Diagnosing and Fixing a Noisy Alternator [2024]

Car owners are all too familiar with the fact that certain parts of their car may fail at times.

This is why many of them try to make sure the car receives regular maintenance so that the chances of parts failing are next to none.

However, no matter how hard you try or how regular your car receives maintenance does not guarantee that a part will not fail.

One part that seems to almost always go bad or create problems is the alternator.

Alternator noise is the first sign that your alternator is going bad.

It is usually the culprit behind many of the electrical failures in your car.

In this article, we will discuss the ways to properly diagnose the issue and how to fix a noisy alternator, or if it is time to replace the unit.

What is an alternator?

While most people have heard of an alternator, many aren’t sure what it looks like or what it does exactly.

Cars are wired with sensors and electronics which require power to run.

But how can a single battery power everything? 

It can’t and that’s where the alternator plays a role.

The alternator is a small and lightweight part found at the front of your car engine.

Your battery starts your car and the alternator takes over after to power everything else while charging your battery at the same time.

A belt spins the pulley on the alternator thereby generating electricity.

Common causes of alternator noise

Worn alternator bearing

A belt on your engine spins the alternator pulley and that genres the electricity the electronics in your car needs to function. 

This action heavily relies on the bearings to keep everything running smoothly.

After many hours of spinning at high speeds and traveling many miles, the bearings may start to become worn. 

bad alteranator bearing

Loose or worn alternator belt

The serpentine belt as it is rightfully called is the alternator belt that passes through several pulleys on the engine. 

While the engine runs, the belt pulls those pulleys as well as the alternator pulley and makes them spin.

Due to constant friction, the belt can become worn over time and may need to be replaced.

Read this article on how to stop a squeaky belt if the serpentine belt is loose, worn or damaged.

Loose alternator bolt

Vehicles are used every day and sometimes the road may not be the smoothest. 

This means the car will experience tons of vibrations which can cause things to loosen up.

Signs of a bad alternator 

Warning Light

Conveniently most cars built in the last decade feature a warning light on the dash that alerts you of alternator issues. 

In some cars, the warning light is shaped like a battery while others may show “ALT” or “GEN” to let you know something is amiss.

The light works by linking up to the systems in the car that monitors the output voltage of the alternator.

If the voltage goes above or below the preset limit, the warning light on the dash comes on.

Dim lights

Your car’s alternator is responsible for powering your headlights as well as other electrical components. 

If you are experiencing erratic symptoms like extremely bright headlights or dim lights it means that there is an issue with the alternator.

You may notice things like your radio going off or seat warmer turning off before the lights go dim.

This is a safety feature that manufacturers implement so you can safely pull over before your light dims and fades.

If that happens you cannot see clearly to pull in the corner and stop.

Flickering lights

Your alternator is built to power a variety of electrical elements but if your alternator is dying, then certain functions will not have enough power to work.

If you find that your light goes from bright to dull then bright again the issue is definitely the electrical system.

To check to see if it is the alternator, turn on the radio or something that uses electricity and see if your light flickers then.

If it does, then the alternator is indeed the culprit.

Dead battery

The alternator works to recharge your car battery while you drive so a dead battery could mean that it is not recharging properly.

Sometimes a dead battery may just be because the lifespan of that battery is up and it is time to replace.

However, if you have a fairly new battery and find that your car won’t start, then it means there’s an issue with the starting system including the alternator.

Your car battery’s purpose is to simply start the engine and get everything running and then your alternator takes over and power everything else.

To check the battery or alternator problem, simply jump-start your car and remove the cables as soon as you can.

If it’s an alternator issue, the car will die again soon.

If it’s a problem with the battery, it will continue to run.

Strange sounds

If there are no visible signs that your alternator is going bad, you’re bound to hear some strange noises.

Listen for any whining, grinding, knocking, or squeaking sound.

Check the other section of this article where we discuss the different sounds you need to listen for and what they mean.

These sounds can also be heard if your wheel bearing is going bad too so read this how long will a wheel bearing last after it starts making noise to sort out that issue.

If there is a ticking noise, then consult this lifter tick article.

Strange Smell

Another tell-tale sign that the alternator has a problem is the smell.

If your alternator is working way too hard and is close to overheating, you will experience a burnt rubber smell.

The rubber smell can also mean the rubber belt is going bad, isn’t aligned properly or there is too much friction when spinning.

It can also mean the wires attached to the alternator are burning.

Not every strange smell means your alternator is going bad but it is recommended to have your car checked out as soon as you experience any strange smells.

Car stalling or difficulty starting

One of the first symptoms of alternator trouble is when your car stalls or has difficulty starting.

While other mechanical issues can cause the issues it is essential to pay attention to everything else going on with your car before you can point your finger at the alternator.

To figure it out, run the same test that you’d perform on a dead battery to pinpoint the part that is causing your car to stall.

Malfunctioning electronic elements

If you find power windows are taking a long time to open and close, then the alternator may be going bad.

Other issues can include a stuck sunroof if you have that, power locks, and power seats taking a long time to respond.

You may even notice the lights on your dash and console dimming or flickering.

What does a bad alternator sound like?

If you’re wondering what a bad alternator sounds like, you must read this section and we go through the different sounds and what they could mean. 

Whining noise

Failing alternators tend to make a very high-pitched whining sound.

You’ll be able to hear the alternator whining noise when accelerating since doing so raise the pitch of the sound.

Grinding noise

You may hear a loud grinding noise coming from the engine compartment.

If you rev your engine and the noise gets louder then it’s probably an alternator problem where a bearing may have become too worn.

noisy alternator diagnosis

Squealing or Squeaking noise

Alternator squeal or squeak similar to the whining sound will increase as you accelerate. 

These sounds may not be as common and heard as frequently as a whining or grinding sound but can also be a sign that your alternator is going bad.

Another way to test for squealing or squeaking sounds is to do it when your car is off.

Turn the alternator pulley by hand and if it squeaks then it’s time to replace the bad alternator bearing or the alternator.

Knocking Sounds

There are several reasons for the knocking sounds that you hear including a broken belt, a broken bearing, or a loose bolt.

These broken or loose parts will bounce around the engine compartment and bump into other parts to produce that knocking sound you hear.

Fix alternator noise

Now that we know the common causes of alternator failure, the signs, and what to listen for, we will now discuss how to go about fixing alternator noise.

Test the Alternator

To make sure that your alternator is indeed the problem, all you need is a simple voltmeter.

To test, set your voltmeter to read DC voltage and connect the leads to the battery terminals.

A reading of 12.6 should pop up if your battery is properly charged.

You can test the battery while the engine is running as well but be sure that the lights and accessories are turned off.

If you get a reading anywhere between 14.2 to 14.7 volts that means your alternator is working well.

If it is higher, it can cause the battery to overheat which can cause some serious damage while a lower reading means that the alternator cannot power your vehicle and needs replacing.

Check the state of the belt

Serpentine belts are made from EPDM rubber so there are no visible cracks to let you know it is time for a replacement like the older belts that were made from neoprene.

To determine if the alternator belt is due for replacement is to check for visible signs on the backside of the belt.

Another way to tell is to measure the size of the grooves on the belt.

A small plastic gauge is used to measure the size of the grooves and if the gauge can move when it’s in the grooves of the belt, then the belt needs replacing.

Tighten bolts

Due to the many vibrations and jarring that your car experiences in its day to day operations, a few bolts may loosen while others may come off completely.

This is pretty easy to fix and simply requires you to put the screw back in place and tightening it using the correct sized tool from a socket set.

There should be around three or four bolts holding your alternator in place.

Replace the serpentine belt

If the serpentine belt is worn out, then it is time to replace the belt.

This is also an easy fix that requires the correct belt for your car and a socket set.

Since the belt runs through many pulleys, it can get quite confusing so take a picture of the belt set up before removing it.

This way you can see how to fit the new one and avoid making any mistakes.

To replace the belt, locate the tension pulley first.

This pulley will have a nut in the center so use your socket wrench to turn it which will move the pulley and loosen the tension so that the belt slips off easily. 

Wrap the new belt in the same manner around all the other pulleys and pull the tension pulley out using your socket wrench and slip the belt over it.

That’s it, you’re done replacing the belt.

Replace the alternator bearing

Although replacing the alternator bearing is a bit harder than the other fixes we’ve discussed, it is possible to do it yourself.

This can save you quite a few dollars and honestly who doesn’t like saving money?

To replace the alternator bearing, you will have to remove the entire alternator.

Disconnect the battery first before touching or doing anything.

Nest remove the serpentine belt and disconnect the wire harness from the alternator.

After that, loosen and remove the bolts that hold the alternator in place to remove the entire unit and move it to somewhere that you can work on it without trouble.

Remove the large nut that is on the alternator pulley.

Then remove the bolts and screw that hold the outer plate of the alternator.

These would be at the back of the alternator.

Once the outer plate is removed, remove the housing bolts and screws that are on the outside.

Be careful when doing this since the bearing is usually pressed into the housing of the alternator.

If it still gives you a hard time, you can hit the shaft to remove the bearing assembly.

Just don’t hit it with a lot of force.

Once the bad alternator bearing is out, replace it with the new one and reassemble and reinstall the alternator.

Replace the alternator

Going to the mechanic can cost you a whole lot.

Doing it yourself, however, saves you a ton because you are just paying for the part and there is no labor cost.

Disconnect the battery and remove the serpentine belt by moving the tension pulley to loosen the belt.

Disconnect the wire harness and remove all of the bolts that secure the alternator.

Remove the old alternator and replace it with the new one.

Screw it back in place and attach the wire harness.

Put the serpentine belt back onto the tension pulley and reconnect the battery.

If you aren’t confident to do any of these fixes on your own then pay a visit to your mechanic. 

How long can you drive with an alternator making noise?

So how long can you drive with an alternator making noise?

There is no possible way to tell how long you drive with a bad alternator.

In some instances, it may go months making noise and nothing else happens.

On the flip side, it may fail the very next time you start your car.

In the event, you hear noise coming from your alternator, follow the guidelines in this article to diagnose the problem.

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