By Tsukasa Azuma
Last updated Dec 31, 2020
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Your car battery or charging light on the dashboard of your car indicates a malfunction in the battery circuits or bad charging of the car battery. The light provides you with a warning when the charging system is not charging the battery with the right voltage. However, the warning happens due to many reasons, so it is vital to take the proper steps to know the actual issue before trying to replace any components. One of the problems, which many car drivers face, is when the battery light on but alternator is charging.
Why Battery Light On But Alternator Is Charging
In case the battery light stays on when you start the car, do not worry. It is usual for the light to power on when you turn the ignition to your vehicle. Usually, the light turns off after some time, but if it stays on even when you are driving, then pay attention.
You might notice some signs of a weak battery, including power windows not coming up, or the audio system not working. Let’s perform a few checks to see where the problem lies.
Check for Corrosion
In some car models, the fumes from the regular functions lead to corrosion to collect on the battery terminals. It happens particularly during summer or during warm weather. We recommend you instead remove the covers from the terminals located on top of the car battery.
The presence of a white or greenish substance on the top of the battery or near the terminals is a clear case of corrosion. The corrosion can interrupt the conduction of electricity from the array to the car. Remember not to touch the corrosion with bare hands, as it can lead to skin irritation. It is the first step to help you resolve battery light on but alternator is charging issue.
READ MORE:
- The Comprehensive Guide to Removing Car Battery Without Any Hassle
- How Much Time Does It Take to Charge a Car Battery
Clean the Car Battery Terminals
If you notice some corrosion or grime around the battery terminals, it might be the reason why the car battery light is still on. A significant advantage is that it is easy to clean the battery terminals using standard grease. What you need to do is remove the battery terminals, remove the battery cables, and clean the battery terminals.
Tighten the Battery Clamps
At times, the battery light remains on due to a weak connection between the car battery and the cables that connect to it. Ensure the clamps fastened to the battery terminals. In case you notice the clamps are loose, then use a small wrench to tighten them until they completely cover the terminals.
The car battery is a vital component that provides the vehicle with the necessary power to run on the road. Apart from the issue of battery light on but alternator is charging, you might encounter quite a number of problems with your battery or your alternator that is causing your car slow to start. Refer to these ultimate guides How To Test A Car Battery With A Multimeter and How to Test an Alternator: The Complete Guide to familiarize yourself, which you must, with these critical components in your vehicle.
The vehicle’s electric system consists of a few components, but it keeps the entire vehicle functional, with hundreds of components reliant on electric power.
The battery light comes on when there’s an issue with the system and can be caused by a bad alternator, battery, or cables. The charging alternator should not be ruled out, as it can still deliver incorrect voltage to the battery.
Battery Light On – Causes and Solutions
The battery light comes on when there’s a problem with the battery’s power. It can be caused by lack of charging, low charge, but also bad connections and voltage.
1. Corroded Battery Terminals
When the battery is okay and the alternator is charging, corroded battery terminals are the most likely cause.
The connection between the battery and the vehicle’s cables becomes unstable and intermittent, which is reported by the computer.
How to Fix Corroded Battery Terminals
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Fortunately, the fix for this issue is incredibly simple. All you need to do is disconnect the battery and use the brush on the battery terminals and the wiring clamps.
Get rid of the white and blue deposits and reconnect the cables. If necessary, clear the error code and the problem will go away.
2. Bad Wiring
Bad wires can cause a number of problems with the vehicle, and if that’s the case, the battery light will be the least of your issues.
The engine bay is a maze of wires, pipes, hoses, and belts, so unless you remember the part you’ve worked on or might have damaged, it’s better to let a professional handle the problem.
How to Fix Bad Wiring
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The issues with the wiring can be fixed by cutting, extending, and soldering. A good trick for extending the wires is to line up about 1/4″ of exposed wires in parallel, twist them together, then insulate them with tape.
Soldering is more complicated than it looks, and often the soldering wire will refuse to bind the two parts. If you have experience with a soldering iron, there should be no problems, but if not, I suggest practicing a bit before working under the hood.
3. Overcharging Alternator
Your alternator may seem like it’s working correctly, but until you’ve checked the voltage and confirmed it’s not overcharging, you can’t be sure.
The alternator overcharge is a common problem where the current regulator fails, causing the alternator to deliver more power than necessary. This issue should not be neglected as it can lead to permanent battery damage.
How to Check Alternator Charge
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Measuring the voltage delivered by the alternator is a very simple process. First, you set the multimeter to 20 volts DC to get the correct reading.
Turn on the engine and measure with the test leads over the battery – the red probe goes on the positive battery terminal and the black goes on the negative terminal.
The multimeter should read 14.2 to 14.7 volts. If it’s beyond the upper range, it means that the alternator is overcharging. Lower than that – and it’s not charging enough.
In both cases, the correct course of action is to consult with a professional on how to address the issue.
4. Dying Battery
When the battery goes out completely, you won’t be able to start the vehicle and the cause will be obvious. However, there’s a period when the battery is on the verge of dying without you realizing it.
The vehicle might need an extra second to start, and as the alternator is working correctly, it’s going to keep the battery operational for a few weeks or even months depending on how you drive.
How to Check Battery Charge
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Checking the battery voltage is done in the same way as checking the alternator, so you might as well check both at the same time.
With the car turned off, open the hood and locate the battery. Set the multimeter to DC voltage. Place the red test probe on the “+” of the battery and the black probe on the “-“.
If the reading is below 12.2 volts, it means that your battery is going out. With the alternator ruled out, we’ve identified the battery as the cause and it’s just a matter of replacing it.
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5. Worn Serpentine Belt/Alternator Pulley
The combination of a bad serpentine belt and or alternator pulley can also cause issues with the electrical system.
A bad alternator pulley will cause an unnecessary load on the engine, while a bad serpentine belt will cause the alternator pulley to slip and fail to create stable power.
How to Check the Serpentine Belt
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One of the main symptoms of a bad serpentine belt is squealing noise when the engine is cold. Additionally, you can visually inspect the belt – it doesn’t take an expert to notice cracks and worn threads in the belt.
How to Check the Alternator Pulley
The alternator pulley issue will reveal itself at certain RPM, mostly when the car is idle. The noise sounds like electric sparks from the movies – a high-pitched, intermittent creaking.
If you determine the alternator pulley as the cause, it’s better to let a professional handle it rather than working on it yourself, as the pulley is hard to remove and mount back on the alternator.
FAQs
Why is my battery light on with a new alternator and battery?
A new battery and alternator should be enough to fix the battery light problem, provided that you’ve also checked the serpentine belt and the battery wires.
It’s possible that the error code has to be reset manually even when the problem is solved. To do this, plug in an OBD2 scanner, find the battery light code and clear it.
As long as it doesn’t come up again, you can be fairly certain that you’ve solved the issue.
Can a blown fuse cause the battery light to come on?
It’s possible, but unlikely for a blown fuse to cause the battery light to come on. When a fuse fails, one of the electrical components will stop functioning, and you’ll get the check engine light.
Can the alternator cause the battery light to come on?
The alternator is an essential piece of the electrical system, and a problem with the alternator will cause the battery light to come on. By reading the error code, you’ll be able to tell exactly what the issue is and then you can resolve it.
How do you reset the battery light?
Resetting the battery light can be done in two ways: either with an OBD2 code reader or by disconnecting the battery.
Plug the reader/scanner into the OBD2 port and set the ignition to the On position. Navigate the scanner’s menus until you find the battery light code and clear it.
If you’re clearing the code without a scanner, you’ll have to disconnect the battery and wait 5-30 minutes for the ECU to drain completely. Once you reconnect the battery, the error code should be gone.
What fuse controls the alternator?
The position of the alternator fuse, or more likely the alternator relay depends on your vehicle. To get its location, you’ll have to reference the owner’s manual.
What does it mean when the oil light and battery light both come on and the car dies?
It’s very unusual for both the oil and battery light to come on at the same time. Even if the battery is dying, it shouldn’t have an effect on the engine’s operation until the very end.
It makes a lot more sense for both the lights to be accompanied by distorted sound from the radio, lack of AC, dim headlights, and incorrect dashboard readings. Those are the symptoms of a dying battery, with the last phase being the shutdown of the engine.
How long does it take for a battery light to reset?
The battery light comes on when the computer registers a problem, but it can also go away if the problem is intermittent. There’s no defined time for the battery light to reset, as it can happen after a few minutes, hours, or never.
If you’re asking about how long the battery should be disconnected to clear the light, around 30 minutes should be enough.
Can low oil mess with the battery?
The battery and the engine work together in the complex powertrain system, but low oil won’t have any effect on the battery.
Summary
When the battery light comes on, there are a lot of potential causes that don’t include the alternator. Bad and corroded wiring, loose battery terminals, dying battery, and a blown fuse are among the most common causes.
Here are some other articles to read:
What Causes Alternator Overcharging And How Do You Fix It?
3 Wire Alternator Wiring Diagram
Symptoms of Loose Battery Cables