10 Signs Of A Bad Alternator

If you start having issues with your alternator, you will first notice two signs before others will begin to manifest. Your dashboard light will be on for a short time, probably as faint headlights, or some flashing gauges.

Secondly, your vehicle could develop a bad odor and a frustrating sound from beneath its hood.

The two problems above are among the several signs of a bad alternator. Therefore, you need to look into it and strive to solve this issue or replace the bad alternator to limit or prevent it from causing potential problems to your car, beginning with sluggish acceleration to a condemned car.

Signs Of A Bad Alternator

Signs Of A Bad Alternator

There are several situations when a bad or failing alternator develops some signs before it completely fails. Therefore, immediately you notice these common symptoms, it will help you identify the problem a lot quicker and find a solution that will reduce the risk of expensive repairs.

1. Car Won’t Start

One of the most common signs of a bad alternator is a car that stalls or won’t start at all. Most car owners forget that their vehicles don’t just run on gasoline but are also powered by electricity.

The latter is where the alternator comes in, as it is crucial in providing power to the spark plugs that start the engine.

If an alternator becomes bad or fails, it will stop producing sufficient power that the spark plugs need to enable the engine to remain active, thereby making the engine stall for no just cause while running or to experience difficulty igniting.

Neglecting this symptom is at your peril, as it makes your car stop starting completely.

2. Dim Or Very Bright Lights

Dim or excessively bright light is also one of the most common signs of a bad alternator.

Remember, the alternator gives power to the headlights; so, the dim, flickering, or overly bright light shows that the alternator can’t perform properly.

Whenever a vehicle alternator begins to fail, it starts giving an irregular voltage to the car’s electronic components. Here, it comes in the form of over-performing parts, such as the headlights, which are either too dim or too bright.

Sometimes, you will either notice flickering lights or lights that go from dim to bright and the other way round.

3. Dead Battery

Sometimes, a battery can fail on its own, especially when it has gotten to the endpoint of its life, or maybe you must’ve forgotten to turn the headlights off throughout the night.

On the other hand, a bad alternator can kill a battery. For the alternator to become bad, that means it has automatically become ineffective and can’t charge the battery.

In other words, a bad alternator will no longer be able to charge your car battery when the engine is on, thereby causing the battery strength to drain faster, and this is one of the signs of a bad alternator.

Therefore, always check your alternator if you are replacing your battery to know the actual cause of the problem, so it doesn’t occur again.

4. Slow Or Malfunctioning Accessories

Suppose you find out that your alternator is not providing enough power to your vehicle’s electronics.

In that case, you should quickly rectify the problem, as it is among the signs of a bad alternator. A bad alternator can cause other parts to run slowly or malfunction completely.

A bad alternator can also make your car windows hard to wind up or down, cause your seat warmers to feel off, or cause your speedometer and other parts to stop working.

Many current cars come with important accessories, which serve as indicators to the onboard computer where it can first cut power if the alternator stops supplying sufficient electricity.

This results in failed radio or other less important parts and, subsequently, headlights.

5. Frequent Stalling

Just as we have earlier stated, if you find it difficult to start your engine, the most obvious explanation is that the alternator couldn’t completely charge the car battery.

In other words, once you turn on the ignition, the only sound that you will hear is a clicking sound.

However, if your vehicle is frequently stalling when you are driving, it means that the spark plugs couldn’t get sufficient energy from the alternator to maintain the engine’s movement; therefore, it is one of the signs of a bad alternator.

6. Growling Or Whining Noises

Strange noises from your car can also be one of the signs of a bad alternator. Some vehicle noises are harmless, while others might be a sign of critical mechanical problems, including the one caused by a bad alternator.

A bad alternator can fail some of the engine’s bearings, thereby producing some weird rattles.

It could be growling and whining noises, which occur when the belt that turns the alternator’s pulley is not properly aligned or is caught on the sides of the pulley. Once this occurs, an experienced mechanic is needed.

7. Smell Of Burning Rubber Or Wires

If you are in or around your car and you happen to perceive a smell of burning rubber or wires, you should check your alternator to see if its parts have started wearing out.

Remember, the alternator has a drive belt that regularly undergoes tension and friction and is close to the hot engine.

The constant tension and friction could cause them to wear out and ooze out the bad smell from its burnt rubber.

Therefore, when your alternator is overstressed or has damaged wires, you will perceive a burning odor like that of a fire.

It tries to produce excess electricity on all cables, thereby making the wires hot and risky. This is one of the signs of a bad alternator

Also Read: How Much Really Does An Alternator Cost?

8. Battery Warning Light On Dashboard

Most of the time, a red battery alert on the dashboard is associated with battery problems. However, this alert could be a warning sign that something is not right with your general power system in your car, including the alternator.

The alternator operates on a certain voltage, often around 13-14.5 Volts.

Once your car alternator stops working, its voltage could go very low in capacity, thereby initiating the battery red alert sign on the dashboard.

The warning light could also come up when your alternator has gotten to its voltage limits, based on the amount of hard work it has gone through.

9. Bad Belts

Bad or worn-out belts are one of the signs of a bad alternator. Most people fail to give proper attention.

We need not remind you that no matter the defiance you might exhibit on it, bad or worn-out belts remain one of the most notable signs of a bad alternator.

A belt is supposed to possess the right tension to operate the alternator in the best way possible, as too much tension and lack of it can be detrimental.

That is why it is good to sometimes carry out a fast test of its tension, to know the problem. Also, ensure your vehicle is cool enough before starting anything under the hood.

10. Broken Or Loose Connections

Suppose you have checked everything in your alternator and nothing seems to be the problem. In that case, the battery is still not functioning, and most of your vehicle’s electrical components still don’t work, the only explanation left is a bad alternator.

This is because the alternator is generating power, yet, it isn’t generating any electricity or is not the right type.

An alternator generates its power via cables that are big and small wires. Therefore, any problem with the cables, wires, or connections on any side tends to stop electricity flow.

At times, the symptom of this issue can be brighter lighting, as the alternator produces more energy to oppose the resistance initiated by the damaged wire or loose connection. 

We are now going to look at how to test an alternator and tell if it is bad

Also Read: Alternator Repair Options And Which You Should Choose

Frequently Asked Questions

How does a car act when the alternator is going out?

When the headlights of your vehicle dim or flicker it could be a sign of a bad alternator. The lights may get brighter as RPMs increase and dim as the RPM fall. This indicates that the alternator isn’t producing sufficient power to keep pace with the car’s electrical needs.

How do you tell if it’s your alternator or your battery?

A simple method to determine if the alternator is operating is to start the car and disconnect the positive end from the battery. If the car stops operating in the middle of the road, you may have a defective alternator. Also, check your dashboard and interior lights.

Can a car run with a bad alternator?

A car can run for a brief period when the alternator is damaged. The battery charges the alternator while the engine is in operation. However, when the battery has exhausted, the car will stop running and not start.

What sound does a bad alternator make?

Whining and Grinding Sounds
If your alternator has stopped working, it could be causing a couple of unusual sounds. If you notice a tiny grinding or rattling sound while your engine is running, it may result from the loose bearing in the alternator.

Can a bad alternator destroy a new battery?

An alternator that is failing can cause overcharging, which can damage the battery. If the alternator isn’t charging properly, it will leave the battery uncharged and accelerate its demise.

Do alternators fail suddenly?

The alternator is an essential component of the electrical systems that are in your car. If your alternator starts to fail, it could cause many different electrical problems within your vehicle that can eventually lead to the breakdown. Alternators may fail quickly or gradually in the course of time.

How much does it cost to fix an alternator?

If your vehicle is experiencing electrical problems, that’s an indication that you require replacing your alternator. If you consider the price of an alternator replacement and the labor involved, it is recommended to pay between $500 and $1000 for a brand new one for your car.

Can I change an alternator myself?

Repairing an alternator can cost you hundreds of dollars at a repair shop in your neighborhood; however, it’s among the easiest repairs you can perform at home. With just a few tools and a little more than an hour, you can replace it yourself and keep the money in your pocket where it belongs.


For easy and timely servicing, it is important to be alerted to the signs of a bad alternator. You can visit any experienced auto mechanic for proper maintenance or repairs if required to prevent the aforementioned symptoms from resulting in more disastrous consequences on your car.

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