10 Symptoms of a Bad Alternator Belt & How To Replace It

​Apart from the engine and the wheels, there are many other parts in a vehicle that make it run. Not only you will find combustion systems and transmission parts that help the car move, but you will also see those electrical parts that need to function correctly or the car won’t do its job.

Among these parts, you will find the alternator.

But the alternator is not a simple component. It depends heavily on the that pumps the battery energy to power up other parts of the car that are essential for its operation. When this belt fails, the car will most likely fail too.

Here, we are going to show you all the problems you can experience when this alternator belt starts to fail as well as a guide on how to fix plus a little more.

If you are excited to learn how to fix your defective alternator belt, then take a step further to find out!

What is an Alternator Belt?

It all starts with the alternator. This component sustains electrical power from the battery all around the car into several electrical components. Without the alternator, the battery wouldn’t be able to power up all these components, as it won’t have enough power. And thus, the car won’t function correctly.

The entire purpose of the alternator is to keep the power going all around the car, as well as augmenting the charge so the most demanding parts can power up. And of course, the alternator does this using a spinning belt.

The process of charging the battery or passing the electrical charge throughout the car is done by this spinning belt. It wraps around a pulley which eventually connects to the crankshaft.

When the vehicle is on and the crankshaft moves, it will make the belt spin and charge up the alternator which finally charges up the battery.

All the charge in the alternator eventually helps to power the AC system, the power steering, and the water pump, as well as electronic parts in the dashboard  and more. Without the belt, the vehicle electrical system wouldn’t work correctly – even starting the car would become an issue.

This belt is often described as a serpentine belt, and it is supposed to last between 25,000 and 50,000 miles or around five years in a standard car.

After this time, it will need to be replaced. This happens because it can eventually crack, loosen up, wear out, split, or just break, making the alternator malfunction and the car not to run as usual.

Whether it is of old time or the friction & heat this belt is subjected to, you may experience several symptoms when it malfunctions. That’s why it is essential always to know when this belt needs replacement. So you can keep your car working correctly and prevent any unwanted situation.

10 Bad Alternator Belt Symptoms

There are many ways a bad alternator belt lets you know that it’s time for a replacement. Here are ten issues you can experience when this happens;

1. Lights Start Acting Weird 

When the lights of your car flicker or blink unexpectedly and without reason, there’s a probable electrical issue. Most of these problems start at the battery or with the alternator. This means something is failing to the point of almost shutting down completely.

If the problems with the lights start being consistent with time, it’s very likely the fault of the belt, and it may shut the alternator down completely. This will end up in far worse problems than just lights acting weird.

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2. Weird Noises from the Hood

As the belt is connected directly to the crankshaft, there’s a lot of movement this part needs to do. Especially when the car is idle, the belt will spin at fast speeds, which may eventually cause weird sounds when it is old or broken.

Among the weird sounds, you can experience a squealing or growling noise, related to a slipped or misaligned belt. The noise will be more present and higher when the car is idle or not moving due to a faster movement of the alternator.

Another noise could be flapping that happens when the belt is broken or frayed, and it hits the different metal parts inside the hood.

And finally, you may also experience a ticking sound, similar to the flapping noise, it happens when small pieces of the belt jump around the engine. Both these noise mostly occur when the car is moving.

3. Overheated Engine

The belt helps the alternator create an electric current which eventually powers up parts of the vehicle that cool down the engine.

When the belt doesn’t work correctly, the alternator will fail, and the water pump that cools down the engine won’t do its job.

Eventually, you may experience an overheated engine. You will see how the temperature rises, or you may start seeing smoke coming from the hood.

4. Burning Smell

When the internal wires of the vehicle or alternator start wearing off due to shorting or inconsistent current, they will produce a bad smell of burning.

A similar thing happens when the belt is misaligned or broken, and it starts to cause improper friction with other parts of the engine.

This will produce a smell of burning rubber that’s almost unmistakable of a defective alternator belt.

5. Warning Lights

Sometimes you may not experience anything but a simple battery warning light in the dashboard. This could mean there’s a problem with the battery, but as it is linked to the alternator, it could also be an issue with the belt.

When the alternator belt starts functioning incorrectly, it will immediately harm the electrical system of the whole vehicle.

Thus, the warning system will sense this as a problem of the battery most of the time. So, it will appear as if it is a defective battery, but it is the belt instead.

6. Stalling Engine

This could happen when the belt loosens while the engine is marching, or when it breaks completely. You will immediately experience a stalled engine that could leave you stranded in the middle of the road or eventually make the car lose a lot of acceleration power.

Sometimes it happens that’s just the belt loosening or separating from the pulley or alternator, but sometimes it means it is broken or cracked.

7. No Ignition at All

The alternator is one of the most critical parts of the car, not only because it fires up several components, but also because it has a crucial role in the ignition system. When the alternator charges the battery, this one sends the current to the spark plugs so the combustion can happen.

When the belt is not doing its job either by loosening or breaking, there’s a high chance the alternator won’t send the charge to the battery. Then, the battery won’t conduct the necessary current for the spark plugs in the combustion chamber to ignite the gas.

This will leave the car wholly unusable and demands an immediate replacement of the belt.

8. Defective Power Steering

You may think that the steering wheel of a car doesn’t need an additional system to work more than the crankshaft and the CV axles in the wheels. But in reality, there’s a significant electrical component called the power steering system that softens up the direction process of the wheels.

Without this component, steering can be a huge problem.

And surely, when the alternator belt is not doing its job, the alternator won’t be able to turn on the power steering system in the car. This will eventually leave you with a hard & maybe locked steering system.

9. Defective Air Conditioning

Similarly to other electrical components of the car, the AC system will be immediately affected when the alternator doesn’t do its job correctly.

This mostly happens when the belt is loose or broken, creating little to no current for the AC to function. But a defective Air Cooler could also be the symptom of many other problems, so it is essential to check the car thoroughly before coming to conclusions.

10. Dead Battery

Sometimes your car may not even start when the alternator belt is defective. You may have a little start in the car, but after a few seconds when the battery can’t sustain all the electric power needed for the vehicle, the vehicle will immediately shut down.

This will eventually drain the battery to the point of not delivering any electricity anymore until you recharge it.

How to Replace a Bad Alternator Belt

While replacing the belt is not something that will take the most effort and time in the world, it is still a somewhat complicated thing to do, especially if you aren’t a person versed in mechanics.

However, this process won’t be that hard as long as you follow the right instructions;

1. Check the Belt

Before doing anything to the belt, check it to make sure it needs replacement. Here’s a step-by-step way to test it;

  • Check the tension of the belt by touching it; make sure it doesn’t move too much. If it moves a lot, it means it needs to be tightened up or replaced. The same happens if you try to push it in its track and it moves or falls off, or if it takes too much strength to slide it. This could mean it is too loose or worn out.
  • Use a flashlight to look closely. Any crack or peeling sign will be enough to replace the belt. It is vital to replace it as soon as possible if you see any of these two, as it is likely to break soon.
  • Fraying is also common, so use the flashlight to check the sides of it. There shouldn’t be any sign of fraying or worn out parts in the rubber. If you see any of these, you’ll have to replace it soon, as it is likely to bust at any time.
  • Worn out threads are also very common and one of the main reasons an alternator belt starts to malfunction. Remember that most belts come with a thread that sticks to the pulley and the crankshaft. If the thread is not there, the belt will lose tension and loosen up which makes it work incorrectly. Check with the flashlight to ensure the threads are still there. Replace if they aren’t.
  • When a belt is loose or when it is misaligned, it may eventually touch other parts of the engine. Many of these parts are very hot. This causes the belt to have malformations such as dents, melted parts, or even holes and so on. If you see any of these in the belt, it is time to change it before it’s too late.

These are the visible ways to check your belt, and the ones that will tell you if it needs replacement. If you don’t find any of the previous signs in the alternator belt, there’s a chance it may still work correctly. Otherwise, replace it as soon as you can.

2. Locate the Tensioner and Release It

Now that you found the problem with the belt, it is time to replace it. But before doing this, you will have to take it off first starting with the tensioner.

Locate where the tensioner is first. Different cars will have different designs, but most of them are pretty similar.

Some tensioners are with spring tension, keeping the belt secure and pressured. Others are attached to a rotating bracket bolt in the car or the opposite part of the pulley.

Now that you’ve located the tensioner, you need to use a wrench that fits in the bracket or spring to release the tension. This will separate the tensioner from the belt and release it so you can remove it from the nearest pulley and then from the rest.

3. Analyze the Installation

After removing the old belt, it is important to remember exactly how it was installed. This will help you when installing the new one. If you don’t install it in the right place, you may eventually have trouble.

Memorize as many steps as possible of the belt installation system. From the twists to the turns and each place, the belt passes through. It doesn't take more than a few instants to visualize everything before installing the new one.

Take a picture or video of the removing process so you can have evidence and prevent any issue when mounting the new belt.

4. Mount the New Alternator Belt

The act of replacement means taking an old part and installing a new one. This is what you’ll do here, but it is important to know precisely how before doing it.

Remember to follow the video or process of removing the old belt, but this time in reverse. Twist and turn the new one around the pulleys except the one from the alternator, but always following the removing process.

You should use the wrench or ratchet to adjust the tensioner again. Remember to slip the belt in position around every pulley before doing this.

After adjusting the tensioner, you should release it until it tightens up the belt entirely. Otherwise, use the wrench to adjust it until the belt is ready.

5. Check Everything to Finish

The last step is all about checking the system to make sure the belt is correct.

Push or pull the belt with your hand slightly. It shouldn’t move at all or less than half an inch from its position.

Try to slide the belt using the pulleys. It should slide without much force and without moving too much.

End up by turning the engine on and watching the belt move if needed. You can do this in most cars. Remember to attach any wires or cables to the battery or any other part before starting the car to check.

Alternator Belt Replacement Cost

The replacement of an alternator belt depends on many things, from the brand of the belt to the make, model and brand of the car, to the year, plus other things. However, this could cost from $25 to $200, sometimes a little more or a little less.

Asking a mechanic to do the job for you is also a great idea. This will cost you a lot more than doing it yourself but will take far less time and effort from your side. Usually, a mechanic can charge you as little as $50 for this process, but sometimes it could up to $300 or even more.

This all happens because some cars are easier to access the belt than others. Those cars that have easy access to the belt will take no more than one hour to replace entirely, while others may take up to three hours or even more.


Whatever the reason for replacing the alternator belt and whatever the process you take to do it, you’ll need to do it fast.

If you don’t do it at the right moment, the alternator, wires or even the battery itself may eventually need replacement, and that will be far more difficult and costly than the alternator belt.

If you are experiencing any of the previously mentioned symptoms, don’t waste your time and replace the alternator belt before any more expensive part gets damaged. Do it yourself or hire a mechanic, but do it before it’s too late.

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