Why Battery Light Is On But Alternator Is Charging and What to Do?

One of the problems, which many car drivers face, is when the battery light on but alternator is chargingYour 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.

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.

battery light on but alternator is charging battery corrosion
It is recommended not to touch the corroded terminals with bare hands (Photo: Shutterstock)


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.

Corrosion on the terminals makes the warning light to blink
A white or greenish mater forms on the battery terminals as corrosion (Photo: advanceautoparts)

The car battery is a vital component that provides the vehicle with the necessary power to run on the road. 


  1. Can I continue driving when the battery light is on?

While you can continue driving for a short distance when the battery light is on, it’s not advisable. 

The light warns of a potential issue in the charging system, and ignoring it can lead to a dead battery and a stalled vehicle. It’s best to have the vehicle inspected by a mechanic as soon as possible.

  1. What should I do when the battery light is on but the alternator is charging?

If the battery light is on while the alternator is charging, it’s essential to have the vehicle inspected by a qualified mechanic. 

They can diagnose the specific issue, which may involve testing the battery, alternator, voltage regulator, and electrical connections. Prompt diagnosis and repairs are crucial to prevent further electrical system problems.

  1. Can a weak battery cause the battery light to come on?

Yes, a weak or failing battery can trigger the battery light. If the battery can’t hold a charge properly, the alternator may work harder to compensate, leading to the warning light. 

Replacing the battery may resolve the issue, but it’s essential to have the electrical system checked for any underlying problems.

  1. What other factors can cause the battery light to come on besides a weak battery or a charging issue?

Several factors can trigger the battery light, including corroded battery terminals, damaged alternator wiring, a failing voltage regulator, or a malfunctioning dashboard warning light itself. 

A comprehensive inspection by a mechanic is necessary to identify the root cause.

  1. Is it safe to drive with the battery light on intermittently?

Driving with the battery light on intermittently is not recommended. Even if the light goes off temporarily, it indicates an underlying issue that needs attention. 

Continuing to drive could lead to a breakdown or further damage to the electrical system. Always have the vehicle inspected when the battery light comes on, even if it goes off later.

Check out this video from Leo Mafraji Motors to see why battery light on and whether you need a new alternator and battery!

  1. Can a faulty alternator still charge the battery but trigger the battery light?

Yes, it’s possible for a faulty alternator to charge the battery intermittently or at a reduced capacity while still causing the battery light to illuminate.

This scenario may indicate a problem within the alternator, such as worn-out brushes or a damaged diode, and should be addressed promptly.

  1. How can I tell if the battery light is indicating a serious issue or just a minor problem?

Determining the severity of the issue behind the battery light can be challenging without proper diagnosis. It’s advisable not to assume the problem’s extent based solely on the light.

To be safe, have a mechanic inspect your vehicle to identify the cause and assess the severity.

  1. Is it safe to jump-start a vehicle with the battery light on?

Jump-starting a vehicle with the battery light on is generally safe as long as the battery is the primary issue. However, it’s essential to diagnose and address the underlying problem after jump-starting to prevent further complications.

Final Words

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 to slow start.

Refer to these ultimate guides how to test a car battery with a multimeter and how to test an alternator to familiarize yourself, which you must, with these critical components in your vehicle.