How to Test Alternator by Disconnecting Battery

Your car’s alternator plays an important role in keeping the car working after ignition. Without it, your vehicle would drain its battery, leaving you with a dead battery. The alternator functions by converting chemical energy …

How to test alternator by disconnecting battery

Your car’s alternator plays an important role in keeping the car working after ignition. Without it, your vehicle would drain its battery, leaving you with a dead battery. The alternator functions by converting chemical energy to electrical energy so that you can charge the car battery while it runs. But when the car has a bad alternator, it could be problematic.

This article will teach you simple do-it-yourself tricks on how to test an alternator by disconnecting the battery and ultimately saving you labor costs. Shall we begin?

Signs of alternator failure

As a car owner, you may be confused on how to know if your alternator is failing or just bad batteries. The following are the signs that tell you your alternator is failing or about to fail.

Over and Underperforming Headlight

When your car’s alternator fails or fails, you can expect electrical malfunctions that include dim or over performing headlights. A vehicle with a failing alternator will have a headlight that could unexpectedly move from being dim to overly bright and vice-versa without being controlled. You can also expect the headlight to flicker. In this condition, your headlight can easily go bad due to the bad electric current powering it.  

The problem with Starting Your Car

This is quite obvious to most drivers. We immediately suspect a bad alternator or battery when the car fails to start or stay on. The problem is that when the alternator fails, it cannot charge the battery and the battery loses enough voltage to start the car. Stalling or bad ignition is not always an alternator issue. It could be other mechanical issues like a bad immobilizer.

Disturbing Noise

Sometimes we can tell from how our car sounds that something is going wrong. You should expect whirling or growling sounds when the alternator is bad, or the belt is displaced. Check your car for a failing alternator when you notice this sound.

Burning Smell 

You should probably check the alternator when you notice that strange burning smell from your car hood. Discovering this on time could save your car from further damage. Most frequently, the smell is from the serpentine belt and can be solved by replacing it.

Drained Battery

A drained battery is one of the most common features of a bad alternator. As we have mentioned earlier, the alternator serves the major purpose of keeping the battery charged while being used. Once the alternator is bad, you will experience a drained battery due to the inability of the alternator to charge it.

How to test an alternator by disconnecting the battery

Testing the alternator by disconnecting the battery is one of the oldest and most popular ways of checking an alternator. It requires some simple steps, and you will be done within minutes.

Below are the steps to test your alternator by disconnecting the battery.

  1. The first thing to do is park your car in a safe area, where you can perform this process without any danger. You can use a driveway.
  2.  Proceed to make sure that your vehicle is stable, and then open up the car’s hood.
  3. Go on to the driver’s seat and then start the car engine. If you have a failing alternator, you might have difficulty doing this.
  4. Proceed back to the hood of the car
  5. Disconnect the battery while the engine is still running.
  6. Observe the engine’s running if it was like when the battery was connected.

Once you have completed these steps, the alternator is working fine if the engine continues to run normally. If the vehicle stops running, then the alternator may be bad. A failing alternator will be unable to keep the car running.

For those who want more of a visual step by step guide, the following short video will walk you through the process


Where is the alternator located?

You can find your car alternator at the frontal part of your car’s engine. Its location means the engine can power it using the serpentine belt.

Does the alternator charge the battery?

One primary function of the alternator is to charge your car battery while the car is running. Without it, your car battery will easily get drained and die.

How much does an alternator cost?

You should budget around $100-$400 for a good alternator. Premium brands may cost as high as $1000.

How long does an alternator last?

A good alternator should last between 80,000 and 150,000 miles. Although how long it will last will depend on certain maintenance habits. Practicing good maintenance will improve the lifespan of the alternator.

What causes an alternator to go bad?

Generally, all car mechanical parts are doomed to go bad one day. Such is the fate of alternators. Ware and tear are major causes of frequent use.

How much to fix an alternator?

It costs around $150 to repair a bad alternator. Although we recommend, you replace the alternator instead to give your car a healthy life.

What happens when your alternator goes out?

Your can will not be able to run for long with a failed alternator; this is because the alternator will no longer be able to charge the battery. With this happening, the battery will no longer be able to meet the electronic needs of the car.

How long does it take to fix an alternator? 

When an alternator goes bad, it is advisable to replace it to avoid further damage completely. To return a damaged alternator will take about 2 hours. It also depends on if it will be done by a professional or not.

What alternator fits my car? 

To find the alternator that will fit your car, you need to consider some factors, including the alternator’s model and the make. These factors will guide you to getting the right alternator for your car. Also, consider buying a similar alternator with the OEM part of your vehicle.

Can a car run with a bad alternator?

Yes, a car can run on a bad alternator, but it will show some symptoms that may make driving uncomfortable for you. Some of the symptoms include a drained battery, difficulty in starting the engine, etc.

Final Thoughts!

We recommend that you perform regular checks and maintenance on your alternator. This will save you from being stuck in a difficult situation while in transit. It is why knowing how to test Alternator by Disconnecting Battery is an important skill set that is cost-effective. The process is easy and can be done by anyone without professional knowledge.