Battery Light On But Alternator Is Charging – What’s The Problem

A blinking battery light in your vehicle typically indicates that the battery is not charging or functioning correctly. The battery light will glow if the charging mechanism somehow doesn’t charge the battery with a voltage of more than 13.5 volts while the charging mechanism is running.

Modern car’s charging system contains a battery, an alternator, and an electronic control unit (ECU). Older cars also had a voltage regulator. Battery is an important part that provides the essential power to the car on the road to run. Besides, the alternator turns engine mechanical energy to electrical energy to charge the battery.

Several causes can cause this warning; therefore, it is essential to determine the source of the problem before proceeding with the repair. If you are unsure of what is causing the problem, it is recommended that you get expert assistance.

Whenever it comes to electrically charging the car, there is a direct relationship between the battery and the alternator. Like the CEL (Check Engine Light), the battery light may be summed up in a single word: Panic!

If you’ve noticed that your car’s battery light is illuminated, but the alternator is still charging, and you’re seeking probable causes and solutions, this article is perfect for you. In this article , I’ll go through the reasons why this happens, as well as several solutions to the problem.

One of the problems, which many drivers face, is the battery light on but the alternator is charging. Although it seems simple, the actuality is more difficult. The problem comes from a battery voltage, bad alternator, corrosion or loose electric connection.

In this article, we’ll discuss all about figuring out the reason for your battery lights on while the alternator is charging. Our hardcore information gives a guide to detect and solve your car’s situations. Hopefully, you can easily trace what’s the problem and solve the problem.

Before delving deeper into this topic, let’s start with the fundamentals – the relationship between the battery, the alternator, and the battery light, which we will discuss in the next section. Later on, we’ll go through the reasons behind this and how to remedy it.

Why is the battery light in my car on even when the alternator is charging?

When the red battery light illuminates, it indicates an issue with the vehicle’s charging system, impacting the battery’s rate.

There are several frequent reasons why this might occur, including the following:

battery light on but alternator is charging

When you start the car, the battery light stays on for a few times, so no need to worry. Few moments later, the light turns off normally. But,  if the battery light stays on when the alternator is charging, then pay attention to it. You notice some signs such as battery voltage, corrosion on the battery or loose clamps. Let’s take a glance to see where the problem is hidden.

Battery Voltage:

Usually, a fully charged battery should be around 12.6 volts or more. You can use a digital multimeter to check the voltage of your car’s battery.

But, when the alternator is charging, the voltage of the battery should be 13.5-14.5 volts. Once the battery light is on with the voltage above 13 volts, there’s something wrong with the alternator.

Bad Alternator:

There’s a chance of a bad alternator when the battery light remains on with a voltage higher than 13 volts. First of all, confirm the alternator was bad.

Hopefully, it takes only a few minutes, and you don’t need to remove the alternator from your car. You’ll only need a digital multimeter for the tests. You can use this digital multimeter to check the alternator.

Alternator voltage should be 13.8-14.2 volts. You have to install a new alternator when the voltage is lower than normal. Here are some bestseller alternator you can install in your vehicle.

When your alternator is malfunctioning, your battery lights may illuminate during charging. Dim headlights and the indicators for charging and other modes are all signs of trouble. The battery requires a lot of water to work, and the engine must be cranking hard or slowly to avoid making sounds from the alternator.


Replace the component that has been damaged. It is necessary to identify the specific component producing the malfunction during charging. Alternator difficulties will also cause problems when charging. Correctly identifying the malfunctioning component will make its repair easier since you will know exactly which component must be replaced.

Corrosion Problem:

If you see any sign of corrosion, it can be the cause of why your car’s battery light is still on. The presence of a greenish or white substance on the top of the battery terminal is a sign of corrosion. Hopefully, you can easily clean the corrosion from the car’s battery. You just need a teaspoon of baking soda and a glass of water to prepare the solution. Then use a home toothbrush or bristle brush to scrub the solution on the corroded areas.

In some automobile models, the gasses from the standard functions cause corrosion to build upon the battery terminals, resulting in a short circuit. It occurs more frequently during the summer or in warm temperatures. Instead, we propose removing the covers from terminals placed on the vehicle’s battery.

There is no doubt about it: the appearance of white or greenish material on top of the battery or around the terminals indicates corrosion. Corrosion can disrupt the transmission of power from the array to the automobile.

Please avoid touching the corrosion with your bare hands as this may cause skin irritation. Taking this step will assist you in resolving the battery light is on; however, the alternator is not a charging problem.

Electrical Connection:

You should also check all the connectors and similarly check the fuses. The battery light stays on for the weak connection between the cables. Cables and fuses work to connect between the battery, alternator and the ECU. 

Again, make sure the clamps tighten to the battery terminals. If you find the clamps are loose, then use a Clamp Tightening Wrench to tighten them.

Contacts between the battery terminals and the alternator wires are not making good contact. This might be because they are rusted, simply loose, or deteriorating insulation.

The wiring on the 3-4 wire connector on the rear of the alternator is a little slack. There might be a problem with the wires being loose or damaged.

The Battery Is Not Functioning Correctly

An alternator that is malfunctioning or failing. Has the alternator in your automobile checked out? They might sometimes give the impression that they are working even when they’re not.

The most likely reasons described above are descending from the easiest and least expensive to the most complicated.

When you work your way down the list from top to bottom, you will save both time and money in the process.

Battery Clamps that have come undone

When you don’t tighten the battery clamps down, the poor connection between the cables and the car battery will cause the battery light to remain illuminated until you do.


Wrenches should be used to properly tighten the clamps to ensure that they completely cover the terminals. This should be done using safety gloves. Another option is to take your car to a mechanic and thoroughly inspect it to verify that the clamp is properly tightened. 

While you’re there, you might want them to go over the entire vehicle to see any additional problems.

Car Battery Terminals Should Be Cleaned

If you find any corrosion or dust around the battery terminals, this may cause the car battery light to remain illuminated. One significant advantage is that regular grease can wipe the battery connections, making maintenance a breeze. 

In cleaning the battery terminals, you must first disassemble the battery and then disassemble the battery cable assemblies.

Tighten the Battery Clamps until they are Snug.

The battery light may remain illuminated at times owing to a poor connection between the vehicle’s battery and the wires that connect to the battery. Check that the clamps are securely connected to the battery connections. 

If you see that the clamps are not entirely covering the terminals, use a tiny wrench to tighten them until they have been completely covered.

It is possible to proceed to the alternator if the battery is in good operating order. It is used to maintain battery charge and provide electrical components while running. 

A multimeter reading between 13.6 and 14.6 volts should be obtained during the testing of the device. When the value is less than 12 volts, the battery light on the automobile will illuminate.

In the case of a faulty alternator, there are two probable causes:

Voltage Regulator That Has Failed To Function

A malfunctioning voltage regulator is typically responsible for the alternator’s inability to generate sufficient power or is entirelyor entirely inoperative at low RPM. Depending on the make and model of the vehicle, this component may or may not be interchangeable.

The installation of high-wattage accessories may potentially result in a similar problem. An old car’s alternator is unlikely to be able to manage the increased demand if you install high-wattage headlights as well as rear lamps in it, as an example.

The battery light will illuminate the dashboard if the electrical components draw more current than the alternator can produce.

The Alternator Belt Has Begun To Slip

Another element that impacts the regulator is a sliding alternator belt or an alternator that is on the verge of failing. A loose, worn-out, or broken belt might cause the problem. 

The belt being spilled with some slippery liquid, such as engine oil or brake fluid, is an uncommon, but not unheard of, reasonthe reason for the failure to function.

When the automobile comes to a complete stop, switch the engine on as quickly as possible. There is a perfect chance of hearing a screaming noise because your belt has come loose. If the black belt cannot be repaired, it should be tightened or replaced entirely.

Not only will a faulty alternator cause the battery light to illuminate, but it will also interfere with the operation of a few other critical components, such as the headlights and ignition system. 

If you find yourself in this situation, urgent action is required since if you wait any longer, the automobile will eventually shut down and die.

Symptoms You Must Not Ignore:

Symptoms You Must Not Ignore

Although these are the main reasons for the battery light on while the alternator is charging, you should know other signs. These signs indicate important issues including the two parts.

#1 Bad Battery Signs:

  • Inconsistent interior light, headlights.
  • Corroded or loose connection.
  • Visible corrosion on the top.
  • Lights on but the car can’t start.

#2 Bad Alternator Signs:

  • Warning light on indicator dashboard.
  • Flickering or dim headlights.
  • Face problems to start regularly.
  • Smells or sounds from electrical accessories.

#3 Appliances You Must Needs:

  • Digital Multimeter: You can use a digital multimeter to check the alternator and voltage of your car’s battery. We recommend Klein Tools Or AstroAI Digital Multimeter.
  • Baking Soda: You also need some water and baking soda to prepare a corrosion cleaning solution. We suggested ARM & HAMMER Pure Baking Soda for corrosion cleaning.
  • Toothbrush or Bristle Brush: These two are household tools that are used in daily life. If you don’t have a new one, you can buy a toothbrush or bristle brush to scrub the solution on the corroded areas.
  • Clamp Tightening Wrench: You have to use a small clamp tightening wrench to tighten the clamps. If you don’t have one, you can buy the Clamp Tightening Wrench to tighten them.
  • New Alternator- The Final Solution: You don’t have any other options instead of installing a new one when anything goes bad to the alternator, Here are some bestseller alternators you can choose to install according to your vehicle’s.

#4 Headlights And Other Lights Can Be Dimmed

Having your vehicle’s headlights fade or flicker is another sign that your alternator is failing. If you discover that your lights are becoming dim for no apparent reason, inspect your alternator system to determine the source of the problem. Also, check your battery to see if it has a sufficient charge because it may be below. Check to see if any diodes aren’t working correctly.

#5 Noises Coming From Under The Hood

Unusual noises can be caused by worn or damaged bearings, a faulty serpentine belt, a loose alternator pulley, a loosened belt, or other problematic parts. These noises include rattling, crunching, cranking, and buzzing noises. These noises might originate from your engine or any other portion of your vehicle.

As soon as you see something unusual, identify the source as quickly if possible and take it to a mechanic to have it repaired or replaced as needed.

#6 Battery Or Cables That Have Been Damaged

The breakdown of the battery itself is probably the essential cause of the battery alert light to illuminate. Over time, batteries can be damaged, the terminals can get corroded, and the wires can become dislodged or otherwise damaged.

If this occurs, the battery would no longer store the charge provided by the alternator and would progressively lose its ability to generate electricity.

You can visually inspect the battery for signs of damage or corrosion, but you really should use extreme caution and wear eye protection while doing so. If you have any reason to believe that your battery may be damaged in any manner, we strongly advise that you have it tested by a competent expert.

So, as you’ll see, if your battery indicator light illuminates and remains on, it might indicate anything from a bit of a problem to something that can do significant harm to your vehicle’s engine. However, it’s always best to be prepared than sorry, so don’t overlook that warning light and take your automobile to your local mechanic for an inspection right away.

What Is The Maximum Amount Of Time You Can Drive With The Battery Light On?

Suppose your automobile is not laboring to get into idle or displaying indications of mistiming. In that case, it may be feasible to drive for several days or even weeks with the battery light remaining illuminated in some situations.

According to the severity of the underlying problem, you run the danger of the car’s engine failing to start or just breaking down in the middle of nowhere and when you least suspect it.

Consequently, even if you can drive for many days or weeks, get it fixed as soon as possible, especially if you make long journeys or drive at night.

As you drive, the headlights and heating place an additional strain on the battery, increasing the probability of failing.


Is It Necessary To Replace An Alternator Or A Battery Right Away?

However, a faulty battery will not cause harm to the alternator, but a defective alternator will cause damage to the battery.

Since the automotive battery is not meant to produce electrical energy for extended periods, both parts must be in optimal functioning condition.

Fortunately, standard lead-acid batteries are inexpensive, generally ranging between $50 and $120. Compared to battery repairs, alternator replacements may cost anywhere between $500 and $1000, including labor.

You may be able to fix the alternator rather than having to replace it, as well as a rebuilt alternator, which may be a bit more cost-effective. However, just like with a new alternator, the cost will be determined by the make and model of your vehicle.

How Do I Determine The Output Of The Alternator Or Battery?

To examine the battery’s voltage, connect the leads of the voltmeter or multimeter to the battery terminals.

Battery voltage must fall to roughly 12.6V when the engine is turned off in a healthy vehicle. It is recommended that the battery voltage be raised to 13.5V-14.4V when the engine operates.

Turn on the Audio, the Air Conditioning, and the Headlights

A battery voltage of around 13.5V shows that the alternator is performing well. Your vehicle may also be equipped with a voltage or amperage meter that could be used to measure the power of the alternator or battery.

Can I Drive If My Alternator Is Not Working Properly?

It is possible, albeit it is not recommended. Your vehicle’s battery will not receive an adequate charge, and the engine may stall at any time. If you haven’t gotten your damaged alternator repaired yet, you might consider connecting your battery to a charger between starts to ensure that it has enough power to crank your engine.


The battery is an essential part that provides the power to run on the road. Likewise, the alternator turns engine mechanical energy to electrical energy to charge the battery. 

The battery light is on, but charging the alternator is a common problem many drivers face. The problem comes from a battery voltage, lousy alternator, corrosion, or loose electric connection.

Although it looks simple, the reality is more complex, so you must detect and solve the problem. Hopefully, our problem-solving article gives you a guide to detect and solve your car’s problems. Now, you can detect the peak of the problem and solve the situation. 

Generally speaking, the older your vehicle is, the more likely it may have difficulties with it. As a result, if you keep a spare alternator belt in your car as well as a competent emergency toolkit, you should be alright in the vast majority of circumstances. 

In the case of an emergency, it’s always a good idea to pull over somewhere safe, preferably at a filling station or at the very least away from oncoming traffic just on the side of the highway. 

Remove any non-essential electrical devices from the vehicle, such as the radio and air conditioning, and always keep the vehicle running unless it is overheated. You will be able to continue driving if necessary and reach a service station or auto electrician in this manner.

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