Battery Light On But Alternator Is Charging 

Your car’s battery light should not turn on when the alternator is charging. However, drivers frequently encounter light issues.

The battery light staying illuminated as the alternator charges is a fairly common problem. 

Generally, this happens because of corroded battery terminals, battery circuits, or a faulty alternator system. 

As a result, your car’s battery won’t charge properly. You’d need to learn about the potential issues and possible solutions to ensure that doesn’t happen. 

Reasons Why the Battery Light Is On and Possible Fixes 

You cannot fix the battery light unless you identify the underlying issues. Several reasons go into why the battery light acts up. Find out yours below and fix it immediately. 

battery light on in car

Corroded Battery Terminals 

Dirty or corroded battery terminals keep the battery from charging properly. You can easily spot the corrosion by inspecting the battery terminals. Generally, white or green material buildup on the terminals indicates a problem.

This means the battery isn’t charging as it should. 


Once you locate the battery terminals and find the greenish or whitish substance, it’s time to remove it. Take off the battery cables and terminals and clean them using grease. 

Make sure you wear protective gloves as you do that. Otherwise, you might end up irritating your skin. 

Alternatively, you can call in a professional to eradicate terminal corrosion. 

old car battery

Faulty Wiring 

Faulty wires can contribute to various problems in your car, and an illuminated battery light could be one. The engine bay consists of pipes, belts, hoses, and wires. You must spot the damaged part to fix the faulty wiring problem. 


You must cut, extend, and solder the faulty wire to get it functional. An easy hack to extend the wire is to line together ¼” of wires, twist them, and cover them using tape. 

Soldering may get a little technical because the wires often refuse to bind together. You’ll, however, perform the soldering efficiently if you’re tech-savvy or have DIY skills.

If you’re dubious about your DIY skills, we recommend taking professional help. Otherwise, you may exacerbate the existing wiring problem. 

Once the wire gets fixed, the light will likely disappear. If it stays on, proceed with other solutions. 

Loose Battery Clamps 

Not properly tightening the battery clamps can lead to an improper connection. As a result, the car battery light stays on. 


The only way to fix the loose battery clamps is to tighten them. Wear protective gloves and tighten the clamps using a wrench. This would likely fix the illuminated light, and the battery will start charging correctly. 

Worn Out Serpentine Belt 

The serpentine belt, also called the drive belt, wears over time. While you cannot keep it from wearing out, you can take steps to prevent problems arising from a worn-out serpentine belt. 

There’s no secret sauce to finding the belt damage. You only need to examine the belt to spot the damage and its extent. 


You cannot fix the damaged serpentine belt if it’s worn out beyond repair. So, the only solution to the problem is to replace one. We recommend taking professional help for the purpose if you aren’t proficient with car components. 

Overcharging Alternator 

You may assume the alternator is working efficiently, but it might not be so. You must check the voltage and overcharging to ensure the alternator works correctly. 

It isn’t uncommon for the alternator to overcharge. Generally, it happens when the regular fails, and the alternator provides more power than the required amount. 

You must not overlook this issue as it may damage your battery permanently. 


You can fix the overcharging alternator by inspecting its charge and taking preventive measures if you spot any issues. 

Here’s how to go about it. 

  • Set your multimeter to 20 volts for accurate reading 
  • Turn the engine on and inspect the test leads on the battery. The black probe must be on the negative terminal, while the red one should be on the positive terminal. 
  • The multimeter should show 14.2-14.7 volts 
  • If you notice a reading beyond that, it signifies an underlying problem and an overcharging alternator. 

There’s no easy fix to the overcharging alternator issue, and you must consult a vehicle professional to address the problem. They’ll thoroughly inspect the alternator and fix it to resolve the illuminated light problem. 

car alternator

Dying Battery 

You’ll struggle to start your car if the battery dies out completely. However, there’s a time when the battery is on the verge of going out, and few car owners realize it. 

At this point, your car needs an extra kick to start. Also, because the alternator is working properly, it keeps the battery working for a few days, based on your driving habits. 


Open the car hood to locate the battery. Adjust the multimeter to DC volts. Now, place the black probe on the negative terminal side and the red on the positive side of the battery

If the reading is below 12.2, it signifies a dying battery. So, you’d need to replace your battery to get it working efficiently and fix the light issue. 

Malfunctioning Alternator 

A faulty alternator could be the culprit behind a consistently illuminated battery light. A few tell-tale signs of this problem include: 

  • Illuminating Alt and charge indicators
  • Dim headlights 


The only way to fix a malfunctioning alternator is to fix the damaged alternator part. However, this requires you to identify the precise component causing defects. 

Only a professional can spot the exact component and offer suitable repairs. So, it’s best to have your car inspected by a professional car service company.

Signs of a Poor Alternator System

Your alternator can last around 12-13 years. However, the precise timeframe depends on your maintenance habits. But you’re bound to run into problems due to the natural wear and tear of the alternator.   

The key is to replace the alternator system if you spot signs of a faulty system. Not only will it keep the battery light from illuminating, but it’ll also boost your vehicle’s efficiency. Here are a few signs that indicate a bad alternator system. 

  • Your car battery light stays on 
  • A malfunctioning alternator drains the battery quicker than it should 
  • Your vehicle’s headlights flicker due to a poor alternator system 
  • You hear weird noises under the hood, from cranking to grinding and rattling sounds. 
  • A malfunctioning alternator doesn’t provide efficient power to the spark plugs. This keeps the engine from working correctly. In fact, you may notice that the engine refuses to power up. This could be a dangerous incident while on the road
  • The alternator fails to provide enough electricity to your car. As a result, the power doors, locks, AC, and radio might not function. 

Steps to Avoid Battery Light Illumination as the Alternator Charges 

We aren’t new to the phrase, “Prevention is better than cure.” So, why not take a few preventive measures to avoid getting your car sick to the point of taking it to a professional and paying to get it fixed? 

Here are a few helpful ways to avoid the “Battery Light On” issues or any car problem for that matter. 

Detect the System Problems 

Conducting a quick examination before driving your vehicle is always wise. Yes, inspections can get daunting when running late for office; it’s better than encountering unexpected car issues in the middle of the road. Not only will it squeeze your time, but it might lead to costly repairs and fixes. 

Car experts also recommend taking your car to the vehicle dealer’s shop for regular performance checkups. You can do this monthly, if not weekly. 

Check Your System Regularly 

If you notice the battery light stays on even after replacing the alternator, you must not sleep on the issue. Procrastinating on the problem will only worsen it and might risk your safety too. 

You can take your engine system as an example. When the air-to-fuel ratio is inaccurate, the gas will vaporize, emitting a nasty odor from the exhaust. 

So, this could be an issue if your car battery stays illuminated even after replacing the alternator and the battery. Make sure you check the issue and fix it immediately. 

Listen to the Alternator Noises 

Diodes are a critical component of the alternator. The alternator fails to function when they are damaged. Besides, malfunctioning bearings or rotor shafts may also produce weird noises. 

If you hear whining noises from the alternator, it indicates faulty diodes. Grinding noises, on the other hand, signify bearing issues. 

Fixing the noises and faulty components will ensure the optimal working of the alternator, keeping you from running into illuminated light problems. 

Avoid Overcharging or Undercharging 

Use a Digital Multimeter (DMM) to ensure you never over or undercharge the battery. Following such practices will keep you from encountering battery illumination problems and other battery-related issues. 

Final Words 

An illuminated battery light can be annoying when the alternator is charging. This may happen because of various reasons, from corroded battery terminals to lose clamps. 

Hopefully, our guide will help you get rid of the consistently illuminated battery light and enjoy your vehicle’s optimal performance. 

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