How to Test an Alternator: Complete Guide for DAPPS Lovers

Easily Verify Your Car Battery with These Simple Steps

As a car owner, testing your alternator regularly can save you from the stress of a flat battery and ensure you don’t get stranded on the road. However, many drivers do not know how to test an alternator.

If you are a DAPPS lover, fret not; this guide has got you covered. In this complete guide on how to test an alternator, we will show you how to verify your car battery quickly with these simple steps.


Welcome, DAPPS lovers! Car maintenance is an essential aspect of owning a vehicle. If you’re not careful, your car’s battery will run out of charge. To avoid this, you must understand how your alternator functions and how to test it.

An alternator is an essential component of your car’s engine. It is responsible for keeping the battery charged and powering the vehicle’s electrical system when the engine is running.

This article will guide you on how to test an alternator. The testing process is a simple procedure that can be done with basic tools.

What is an Alternator?

An alternator is an electrical generator that converts mechanical energy from the car’s engine into electrical energy. Your car’s alternator provides power to the battery and the electrical system of your vehicle when the engine is running.

How Does an Alternator Work?

When the engine is running, it causes the alternator’s rotor to spin via a belt that connects the engine to the alternator. This spinning motion creates an electrical current that allows the alternator to generate electricity for the battery and electrical system.

How Do You Know If Your Alternator Is Bad?

The symptoms of a bad alternator include:

Symptom Description
Battery Warning Light This warning light appears on the dashboard and indicates that the battery is not charging properly.
Dimming Lights The lights in your car will get dimmer as the alternator fails to supply enough power to the electrical system.
Weird Smells If you smell burning rubber or electrical wires, it could be a sign of a bad alternator.
Weird Sounds You may hear a whining or grinding noise coming from the engine bay if the alternator is failing.
Difficult Starting Your car may have trouble starting if the alternator is not supplying power to the battery.

What Tools Do You Need to Test an Alternator?

Testing your alternator requires the following tools:

  • A digital multimeter or voltmeter
  • A wrench or socket
  • A wire piercing probe or paper clip
  • A vehicle manual

How to Test an Alternator

Now that you have all the necessary tools, here are the steps to test your alternator:

Step 1: Park The Car in a Safe Place

Park the car in a safe place, turn off the engine, and remove the key from the ignition.

Step 2: Disconnect Your Car’s Battery

Disconnect your car’s battery by loosening the negative terminal with a wrench or socket.

Step 3: Connect the Multimeter

Set your multimeter to DC voltage and connect the probes to the battery terminals. The red probe goes to the positive battery terminal, and the black probe goes to the negative battery terminal.

Step 4: Start Your Car

Start the engine and let it run idle for a few minutes.

Step 5: Test Battery Voltage

With the engine running, check your multimeter’s reading. It should read between 13.5 to 14.5 volts. If the voltage reading is less than 13.5 volts, your alternator is not charging correctly.

Step 6: Rev the Engine

Rev the engine to 2000 RPM and recheck your multimeter’s reading. The voltage reading should increase, indicating the alternator is working correctly.

Step 7: Switch Off the Engine

Turn off the engine and safely reconnect the battery’s negative terminal.

The Strengths and Weaknesses of Testing an Alternator


Testing an alternator is a simple procedure that requires no special skills or expertise. The process is relatively quick and easy to perform, and it can help you identify any issues with your car’s alternator before they become a more significant problem.

Regularly testing your alternator can save you from a flat battery and keep you from getting stranded on the road. A working alternator ensures that your car battery is charged and your electrical system is functioning correctly.


The main disadvantage of testing your alternator is that it requires specialized tools. Digital multimeters or voltmeters may not be readily available for some drivers, making it difficult to test their alternator regularly.

If you are not familiar with your car’s electrical system, it is essential to follow the manufacturer’s instructions and use the correct tools to avoid damaging your car.


1. How often should you test your alternator?

You should test your alternator once a month to ensure it is functioning correctly.

2. Can you test an alternator while the engine is running?

Yes, you can test an alternator while the engine is running.

3. What causes an alternator to fail?

An alternator can fail due to several reasons, including a bad diode, worn brushes, or a broken rotor.

4. How much does it cost to replace an alternator?

The cost to replace an alternator varies depending on the type of vehicle you have and the location you live in. It can range from $200 to $800.

5. Can a dead battery cause the alternator to fail?

No, a dead battery cannot cause the alternator to fail. However, if your battery is not charging correctly, it can cause your alternator to work harder and fail faster.

6. What are the signs of a failing alternator?

The signs of a failing alternator include a battery warning light, dimming lights, weird smells, weird sounds, and difficulty starting the car.

7. Can a bad alternator damage the battery?

Yes, a bad alternator can damage the battery by overcharging or undercharging it.


Now that you know how to test an alternator, make sure to perform the test at least once a month to verify that your car’s electrical system is functioning correctly.

Regularly testing your alternator can save you from a flat battery and ensure that you don’t get stranded on the road. Remember to use the correct tools and follow the manufacturer’s instructions to avoid damaging your car.

If you have any further questions or need assistance testing your alternator, do not hesitate to contact a professional mechanic.

Closing Words

Testing your car’s alternator is an essential part of car ownership. However, it is crucial to ensure that you have the correct tools and knowledge to perform the test safely and accurately.

We hope that this guide has provided you with all the necessary information to test your alternator quickly and easily. Remember to stay safe and follow all necessary precautions when testing your car.

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