How To Test Alternator By Disconnecting Battery? Step by Step

The alternator is an important component of a vehicle’s operation. You may think of it as the car’s brain. Not only does it run on engine power, but it also charges the battery for later use. So, if your alternator goes down in the middle of a journey, knowing how to test it by removing the battery might save you a lot of grief.

Your car will not operate correctly if your alternator is broken, which is a major inconvenience in your everyday commute. There are several different methods for determining whether or not the alternator is operational. For a speedy outcome, several individuals have tried unplugging the battery.

The 5 Common Symptoms of Bad Alternator

Before you begin checking the alternator, be sure to check several indications for confirmation since the fault might be in one of the other components.

You do not want to spend your time if you do not get any early warning symptoms because it will inevitably deteriorate. The following are some of the most typical signs of a malfunctioning alternator:

1. Warning Indicator Light

The blinking of the warning indicator light is the earliest and most fundamental symptom of a malfunctioning alternator. At first, you might be perplexed by the brightness. Check the label to see whether it says GEN on ALT. If the light comes on, the alternator is most likely broken.

2. Dim Headlights

Your vehicle’s headlights may also begin to flicker. The alternator produces electricity to keep the lights on when you start the automobile with the battery. The alternator is in good operating order if the light lights appropriately. However, if your headlight is dim or flickers, your alternator is having trouble charging the battery.

3. Dead Battery

A poor alternator’s performance is likewise reflected in the battery’s performance. If the battery goes dead regularly and has to be charged every few weeks, the odds of a failing alternator being the source of the problem are high.

It is harmed if the automobile charging equipment is not properly installed, resulting in a depleted battery. A faulty alternator may quickly deplete a good battery.

4. Problematic Electrical Accessories

An alternator is a powerhouse that ensures that all of your car’s electrical components are working properly. Whether your radio, air conditioner, dashboard lights, or power windows are not working properly, check to see if the alternator is broken.

5. Weird Smell & Sound

Strange noises and odors might also indicate that your alternator is not in good shape. However, these symptoms might be caused by a variety of issues other than the alternator. However, if you notice any additional symptoms that coincide with alternator problems, you should be cautious. Overheating or excessive friction in the alternator might cause a hot-wire or burned rubber odor.

Frequent Stalling

The battery will not have enough power to start the automobile if the alternator fails to charge it. As a result, you may have difficulty starting the vehicle or experience frequent stalling. This can also happen if the spark plug does not receive the necessary power to run the car.

If you notice more than one symptom from this list with your wheels, do not wait to conduct a fast test to figure out what is wrong.

Common Symptoms of Failing Alternator (Video Review)

Testing the Alternator by Disconnecting Battery

Test Alternator By Disconnecting Battery

So, how do you test the alternator when the battery is disconnected? The solution is straightforward and quick. You can check the alternator’s status by following a few easy procedures.

  1. To begin, park the automobile in a public yet secure location. A driveway can also be used for this purpose. If you have pets, keep them within a safe distance.
  2. Open the hood of the automobile. Double-check that the automobile is in a stable position.
  3. Return to the driver’s seat now.
  4. Start the engine of the automobile. Due to the broken alternator, you may have to deal with some difficulties at this time.
  5. Once the automobile starts moving, get out of the driver’s seat.
  6. Return to your car’s battery now. Remove any rust or dirt that you discover around the battery.
  7. While the automobile is still running, disconnect the positive connection of the battery.
  8. Check to see if the automobile engine is still functioning.

If your car keeps running upon unplugging the battery, it means the alternator is in good condition. The problem might lie in some other part of your vehicle. But if the car stops running, then the alternator configuration is not okay. A faulty alternator won’t be able to power the engine.

Why is This Method Not Safe?

When you remove the battery from a running engine, the alternator’s job is to give electricity to the engine. The car’s battery serves as a buffer, ensuring that the motor system’s power flow is maintained. If the battery is accidentally unplugged, the alternator acts as a backup and provides high-voltage electricity.

The high-voltage energy then passes through the electrical components of the automobile, raising the temperature. Electrical tools worth thousands of dollars might be destroyed as a result of overheating. Furthermore, too much power might cause automobile components to fail. As a result, avoid this testing approach if you do not want to spend a lot of money on replacements.

Alternative Methods that are comparatively safe

Rather than disconnecting the battery, you can use some other methods that are comparatively safe and more reliable. You can use a voltmeter and follow these simple steps for this.

  • Turn on the engine with a multimeter while leaving all of the accessories off.
  • Take a reading between the battery terminals using the voltmeter.
  • Now turn on the electrical components and collect readings in the same manner as before.

If the initial measurement is 14V, the alternator is fine. Even if the second reading indicates 13V, it’s still fine. Any reading that differs from the ones above is indicative of a faulty alternator. During this test, make sure your car is in a secure location.


It would be best to understand why most car owners do not advocate testing the alternator by removing the battery now that you know how to do it.

No matter how knowledgeable you are, it would be best if you first considered the effect and safety precautions. If you suspect your alternator is failing, get expert advice before proceeding.

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