Alternator Not Charging The Battery: Causes and What To Do

An alternator is the power plant in your vehicle. It not only charges your car battery while driving, but it also powers your devices such as the radio. It may fail to charge your vehicle, and you will notice this before or during a trip. Well, in this article, we’ll delve into what causes a car alternator not to charge the battery and what you should do. So, let’s get down to it!

alternator not charging the battery

Read more: Things you need to know about alternator


Why Is Alternator Not Charging Battery?

Here are 10 possible reasons why your car alternator might not be charging your battery:

1. Serpentine Belt Is Dead or Poor

An alternator that lacks a belt and pulley will not function. The serpentine belt might fail due to a crack or simply being old. Furthermore, overtightening the item will cause it to fail. Though cars contain tensioners to keep the belts flexible, it is always a good idea to tighten them thoroughly. Your car’s accessories will not function properly if the belt is not in good condition. There will also be some rattling or whining noises. Such noises are caused by the belt’s bearing not being in good condition.

2. Alternator Fuse Blown

An alternator fuse might blow while starting the automobile or while driving. It occurs as a result of an excessive power surge or aging. The fault is in your car’s fuse box. You’ll notice in the box that some fuses aren’t powering up various alternator elements. If this occurs, no current will travel from the alternator to the battery. Surges can sometimes cause electricity lines to burn.

3. A Failing Battery

Such a purpose should be the first thing that comes to mind while starting the car. The alternator and battery work together to power your vehicle’s lights. Your battery may be old or have technical problems. As a result, it will not draw power from the alternator. An alternator allows a car to run. However, it poses a major risk to your car.

If your alternator fails, your battery will consume more power more quickly. When you start the car, you’ll notice this sign. The engine will start but then stop after a few seconds or minutes. You might not be able to start the automobile at times. Your battery will be uncharged, and the alternator will be unable to provide power.

4. Battery Terminal Corrosion

Because of corrosion, your alternator will be unable to charge the battery. It is one of the most common causes of your alternator failing to charge the battery. The chemical or foam corrodes the terminals and prevents them from conducting power. The elements are greenish, blue, or pale in color. Such an occurrence can occur due to an outdated battery, overcharging, or gas or acid leakage. When severe, it can quickly kill the battery.

5. Engine Control Unit (ECU) Error

A smart ECU is standard in most current vehicles. The dashboard allows you to keep track of it. The ECU controls and manages your vehicle’s components, including the alternator. However, if this component fails, the alternator may also cease to function. When the ECU malfunctions, the car’s battery drains, the engine repeatedly stalls, or the car won’t start. A faulty command from the ECU is sufficient to prevent the alternator from charging.

6. Voltage Regulator Failure

Your car’s regulator will not function properly if you do not have this part. Because a regulator maintains a specific charging voltage. As a result, if it fails, your battery will lose power. It can sometimes even blow the car’s accessories and wires. Your car’s lights will gradually become dim or overly bright. When you remove your pedal, the sign becomes more visible. It’s because the regulator isn’t functioning properly. When you test the battery, you will notice that it has a very high voltage of more than 13.7 V. It will receive excessive power from the alternator.

7. Poor wiring

A vehicle with wiring system flaws is risky. It has the potential to do extensive damage, including to the alternator. If you overlook the problem, it may cause your car to fire. The position of each wire is critical. If one of the wires breaks or you don’t properly repair it, the alternator will not charge the battery.

8. Diode Burnout and Leaks

If your diodes have burned out, your alternator will not charge the battery. They’ll perish as a result of overheating, faulty wiring, or electrical overload. Most of the time, one or two diodes fail while the others continue to change power flow. It will worsen once you have loaded your car. More power will be required for the vehicle. However, the few diodes will convert fewer currents and eventually fail. When things leak, the lights dim or go off. When you use a voltmeter, you’ll notice that the diodes are leaking.

9. Oil Spill

An oil spill, though a minor cause, might have an effect on your alternator over time. When you fill-up your oil, it may spill into your alternator. The oil will spread to the inner portions of the alternator as your automobile travels a few kilometers. The oil then sticks, gathering a lot of dust and clogging the alternator. The alternator will not work well if parts such as the brushes become clogged. Expect it to provide little or no power to the battery.

10. Age

Batteries and alternators, like any other electrical device, do not last forever. How long your alternator will survive depends on how you use it and how well you care for it. You can use your alternator for 80,000 kilometers in 7 years. If it falls into this range, the alternator may stop charging. When the alternator has a problem, it will make strange noises. It has the ability to rattle and make a high-pitched or banging noise. The sound depends on the nature of the problem. If the bearings fail, for example, the alternator will wail like a horse. If they die now, the alternator will make a knocking sound.

Read more: How to Check the Alternator in Your Car

What should one do when the car alternator isn’t charging the battery?

When a car alternator isn’t charging the battery, you should follow these steps:

  • Check the Alternator Belt: Inspect the alternator belt for wear, damage, or looseness. If necessary, tighten or replace the belt.
  • Inspect Electrical Connections: Ensure all electrical connections to the alternator are secure and free from corrosion.
  • Test the Battery: Verify if the battery is in good condition and holding a charge. A weak or dead battery can mimic alternator problems.
  • Check the Alternator Fuse: Look for a blown alternator fuse and replace it if necessary.
  • Test the Alternator Output: Use a multimeter to measure the voltage across the battery terminals while the engine is running. It should read around 13.5 to 14.5 volts if the alternator is charging correctly. It’s also possible that the battery terminal corrosion is corroded. So, check if there’s any corrosion on the battery terminals and clean them as needed.
  • Diagnose the Regulator and Internal Components: If the alternator output is abnormal, consider testing the voltage regulator and internal components. Defective parts may require repair or replacement.
  • Seek Professional Help: If you are uncertain about diagnosing or repairing the issue, take your vehicle to a qualified mechanic or automotive shop for proper inspection and repair.


In conclusion, a dead battery might leave you stranded and cause a variety of electrical issues if your alternator is not charging the battery. It’s essential to locate the problem quickly and fix it for your car to operate properly.

To make sure your vehicle’s electrical system runs effectively and dependably, specialist help and diagnostics are advised, regardless of whether it’s a broken alternator, a slack belt, or other connected components. To prevent later, more involved, and more expensive repairs, don’t put off taking care of this problem.


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