Bad Alternator Symptoms – How To Diagnose A Bad Alternator?

Bad Alternator Symptoms – How To Diagnose A Bad Alternator?

August 14, 2021 0 By CarGuy

So you are experiencing an empty battery issue? Your battery never gets full and you are thinking that the battery is bad? Well, let me tell you that this is not always the case. Maybe you are experiencing some bad alternator symptoms.

Alternators are special components that are placed on your engine in order to fill up the battery and produce power for the accessories to work.

Without alternators, you will not going to have any accessory power and your battery will drain very quickly. And this is the case when you are experiencing bad alternator symptoms.

Your battery basically is not holding power and the battery drains too quickly. You feel like something is wrong inside of your electrical components but this is not always the case. Since alternators are prone to failures.

Every owner swaps it’s alternator at least once during his ownership of the vehicle. Alternators usually don’t last for too long and are prone to failures. Most notably their brushes tend to go bad and these alternators have to be rebuilt in order to continue working properly. We are going to cover that in this article and more.

In this article, we are going to discuss alternators. What are alternators and what is their job? How do they work and how do they produce power? Then we are going to cover the bad alternator symptoms that usually occur when you are having a bad alternator. Then we are going to cover the alternator replacement cost. And also, we will see if these alternators can be rebuilt. So, let’s begin!

What Is An Alternator?

The alternator is basically an electrical generator. This generator is turning mechanical energy into electrical energy.

These alternators were firstly incorporated into vehicles that were used in WW2 in order to power the radio equipment. But later as the demand for power in vehicles increased. Since many accessories were invented.

Alternators brought a lot to the table for a relatively cheap price. They replaced the older ways of powering up the batteries and created a new standard. The first car that was equipped with an alternator was the Chrysler Valiant way back in 1960. And since then, every internal combustion vehicle is equipped with an alternator. And the alternators are one of the rare parts of an internal combustion vehicle that has not advanced much throughout the years.

An alternator from the 70s is pretty much similar to a modern alternator from 2021.

The alternator is usually mounted at one side of the engine. It is connected with the battery on one side and on the other is connected with the accessory belt that is powering the alternator with mechanical energy.

What Is His Job?

The alternator is a pretty smart invention, it converts mechanical energy into electrical current. This electrical current works in a way that it recharges the battery and powers a lot of auxiliary systems like the car computer, headlights, radio, and infotainment systems. Basically, everything is powered by the alternator.

And all this is possible by the accessory belt that is driving mechanical energy from the crankshaft into the alternator. The crankshaft is basically spinning the alternator, creating an electric current in the process. This magical process makes all our car appliances work properly.

Bad Alternator Symptoms

Bad Alternator Pictured, Free Stock Photo by Pixabay

Alternators also tend to go bad after many years accumulated on them. These hard-working parts tend to give up and develop symptoms. And we are going to cover the symptoms in the next chapter.

Bad Alternator Symptoms

Alternators like with every other part of our cars develop symptoms when they fail. During their long life, they are exposed to a lot of stress and hard work, and as they age, they are starting to give up and go bad. When you have a bad alternator, you can rebuild it or replace it. We are going to cover that further down the article. But first, let’s see which are the bad alternator symptoms.

  1. Empty Battery
  2. Malfunctioning Accessories
  3. Flickering Headlights
  4. Dome Lights Lose Power
  5. Engine Stalling
  6. Wining Noise
  7. Battery Light On The Dash
  8. Smell Of Something Burning

1. Battery Is Getting Empty Too Quick

One of the first bad alternator battery symptoms is probably the emptying of the battery on your car. If your car battery drains too quickly and you barely have the energy to start your car, you should probably consider checking your alternator and if it’s working properly.

The car battery should be always full and have enough power to start the vehicle. If it’s not full there are three options. It’s either the battery is bad and doesn’t hold electricity. In this case, you are going to need a new battery.

The second option is that you have a shortened-out installation and some component is stealing the power from the battery, like the radio or other components.

And the third thing is the alternator, if the alternator doesn’t work properly, it is not going to give you a full charge and you will be left with 30% or less power on your car.

2. Malfunctioning Accessories

Another symptom are the malfunctioning accessories. If your alternator doesn’t charge you will notice how the dome lights start to flicker or the fan blower motor doesn’t turn on in the cabin. Or your radio and infotainment suspiciously restart.

In this case, case you will probably be thinking that your car is cursed and you are a victim of black magic. But you should not worry, it’s probably the alternator that went bad and doesn’t generate enough power to keep all the accessories on.

3. Headlights Are Flickering

Another symptom of a bad alternator is the headlight flicker. If the alternator went bad you can expect some power shortages and your headlights will probably start to flicker as well.

This will be most notable during the night driving. This can also put you in danger. Just imagine your headlights turn off all of a sudden in the middle of the night.

That’s why addressing this problem on time is the best for you and your car. This will guarantee your safety as well as your comfort while driving.

4. Dome Lights Lose Power

Another in the list of bad alternator symptoms is the dome lights that are left without power. These dome lights might not work if your battery is completely empty and the alternator is barely producing enough energy to keep the engine running.

5. Engine Stalling

Engine stalls are also frequent in some severe cases with bad alternators. Supposing that the battery is empty and the alternator makes zero electric current. It will be extremely difficult to keep the engine running.

There will be basically zero spark in the combustion system because there will be no power to the spark plugs. This will cause your engine to shut down.

This can be extremely frustrating if it happens in traffic or in the middle of nowhere. So, be aware of your battery and alternator health. This usually happens if the battery light is ignored for a long time. But we are going to discuss that in a bit.

6. Grinding or Whining Noises Coming From The Alternator

When your alternator fails, it starts to develop some grinding noises. These noises can happen when the alternator is cold and can later disappear. This is a clear sign of bad alternator bearing.

When the bearing is failing it has also the potential to damage the brushes of the alternator and prevent it from producing power.

So, when you hear some whining noises that come from the alternator it is a good idea to give it a look and inspect the alternator. Because this can be repaired by a technician that is an expert on electrical components.

7. Battery Light On The Dash

The battery light will also appear on the dash since there is no charge to the battery or the charge is pretty weak. This means that the battery does not get enough power and the battery level is low.

This is a clear symptom that you either have a bad battery or a bad alternator. And this has to be further inspected. For example, if you have another battery you can try to troubleshoot the issue on your own.

Replace the battery with a new one and see if the light persists. If the light disappears it means that the previous battery was bad. But if the light still appears it means that the alternator is bad and you are experiencing some bad alternator symptoms.

8. Bad Smell Coming From The Engine Bay

If there is a smell that is coming from the engine bay, the best thing to do is to stop the car right away. If your alternator is not in good condition it can cause a fire. It will eventually overheat and start melting the wires, resulting in a burnt rubber smell.

In this case, the best thing to do is to stop the car and try to put off the fire with an extinguisher if you have one. If you don’t have one leave the hood open and hopefully will stop melting the wires. And will not gonna start a fire.

This is why sorting the alternator or other wiring issues on time is a smart idea. You don’t want your car to burn to the ground because of a few wires.

Bad Alternator vs Dead Battery

It’s very easy to confuse dead battery with bad alternator symptoms because they basically share the same symptoms. But in order to know what really is the culprit for the issue that you are running against you need to troubleshoot.

If you get a battery light on the dashboard then it is a good idea to test with another battery. Get another battery and drive a few days with this battery.

If the battery empties like the old one after few days, it means that the alternator is not charging, and you are experiencing bad alternator symptoms.

If the health of the battery after few days is good and you don’t experience any sort of power loss. Then you are probably having an issue with your battery.

This can be difficult to pull off especially if you don’t have another battery, but it’s the only way to do it. If you can’t perform this check, then visiting a mechanic will be a good idea. He is going to test the alternator and he is going to see how much power is producing.

How To Diagnose A Bad Alternator?

Diagnosing a bad alternator can be tricky. In order to diagnose a bad alternator, you will need a multimeter. This tool is essential when you having bad alternator symptoms and want to diagnose the issue in order to be sure that 100% is the alternator to blame.

Alternator Replacement Cost?

Alternators are parts that are readily in stock in almost every parts store around the country. Also, online there are hundreds of stores that sell alternators.

In order to get the right alternator, you have to look for the parts number. You need the right alternator for your car. If you get a smaller one the belts will be loose or you won’t be able to mount it. Or if you get a bigger one you will not be able to mount the belt.

So, getting the right alternator for your make and model will be the perfect thing to do.

Alternators don’t cost a lot usually. New ones go from $100 and up to $200 depending on the power that you need.

Can Alternators Be Rebuilt?

Rebuilding an alternator is also a possibility. There are many people are rebuilding these at their house. They just replace the damaged parts with new good parts. The process is fairly simple for those how are into electrical subjects and understand how alternators work. If you want to know more, here is a video on how an alternator rebuild is performed.

Risks Of Driving With A Bad Alternator

There are a few risks when it comes to driving with a bad alternator. These risks include engine stalling. This can be really inconvenient if your engine decides to stall in the middle of nowhere.

Also, you are going to have to pay someone in order to pick your car up. This is also expensive.

Another thing is that a bad alternator can cause a fire. It can burn your car to the ground and you don’t want that. Electrical issues and alternator problems should be sorted as soon as possible, immediately after you experience bad alternator symptoms you have to act quickly and tackle the problem in an effective manner.

Alternators after all are not expensive parts and are readily available in your local parts store. Just go and grab one and tell your mechanic to replace it. Simple as that, then you are good to go for 150k+ miles.


In this article, we learned everything you need to know if you are facing a bad alternator issue. We learned what are alternators and what they do, we discussed all the bad alternator symptoms, so you have a clear understanding and what should be your next step.

The next step involves diagnosing the issues with a multimeter and replacing the alternator with a new one. Or possibly rebuilding your old alternator if it’s savable.

If you want to learn more about electrical issues you may also want to check our articles on bad starter symptoms and spark plug fouling. Also we have a lot of content focused on engine issues as well. Namely, front main seal repair cost and bad valve seals.