How to Test Alternator (Information Guide)

How to test alternator Overview

Did you know the function of an alternator in your car? Well, If not, this component is responsible for powering the electrical system of your car, including the speaker, the starter motor, and the lights. How to Test Alternator?

How to Test Alternator (Information Guide)

When your car alternator goes bad or fails, It can discharge your battery and cause issues with your car’s electrical system. It can also leave you stranded when you want to use your car.

Thus, you need to recognize the simple steps you could take to test your car alternator If you suspect It is expecting some problems.


The necessary materials required to test your car alternator are as follows:

• A digital multimeter or a voltage meter
• About three feet of rubber hose
• Safety glasses
• Wheel chocks

How to Test Alternator (Information Guide)

Steps for testing an alternator

Step one: Preparation

Preparing to test your alternator is simple as It can be completed in the following few steps:

  1. Park your car on level ground for comfortable working.
  2. Turn off the engine
  3. Secure the rear wheel chocks in the side of the driver’s side to ensure that your car is not moving.
  4. Wear your safety glasses
  5. Open the car hood.

Step 2: Locating the alternator

An alternator is usually located near the top and the front side of the engine for most vehicles. The majority of the alternators have a vented and a round metal housing and a visible copper wire.

Step 3: Checking the drive belt of your engine

Proper charging of your alternator can be affected by a loose drive belt. As such, the first thing you Check after accessing your alternator is the tightness of the drive belt.

Thus, you need to locate the serpentine or the engine’s drive belt and Check the tightness when you press it between two pulleys. During your inspection, ensure that you have minimized the movement of the belt so that It doesn’t feel loose.

Ensure that you tighten the serpentine belt or the belt properly before you move to test your alternator.

Step 4: Listening to the engine

You can listen to the sounds from the engine to determine where the problem lies. To do so, carry out the following processes:

  1. Start your car engine.
  2. Listen If the engine produces any unusual sounds like squeaking or grinding.
  3. Locate the source of your noises using the length of your rubber hose. You can use the length of your rubber hose as a stethoscope. Place one end on the housing of the metal alternator and the other one on your ear to listen to any noises. If you hear very loud sounds of squeaking and grinding through the hose pipe, It might mean that your alternator bearing is broken. As such, the bearing will need replacing.

Step 5: Alternator testing when the engine is turned off

This is the step that involves the actual alternator testing. The first testing procedure should be done when the engine is turned off. Follow the steps below to complete the testing procedures:

  1. Turn the engine off
  2. Turn the voltage on and set It to the voltage of the DC.
  3. Connect your positive terminals to the positive leads on the battery. Then connect the negative terminal with the negative lead on the battery.
  4. Read the voltage of your battery by reading on your voltage meter. If all is well, the batter will be reading around 12.5 volts.

Step 6: Testing the alternator when you have turned on the engine

In this step, turning the engine on will help you test the alternator when the electrical system is turned on. You will complete the tasks in this step as follows:

  1. Turning on the engine
  2. Checking the reading n the voltage meter. This time, the reading should range between 13.5 volts and 14.5 volts.
  3. Turn on the car’s radio to stress-test the alternator. You can also use the air conditioner and the headlights for this function.
  4. Ensure there’s no reduction in the voltage when the electrical systems are turned on by checking the voltage meter for a second time.

If there is no change in the voltage reading after starting the engine, or when the reading does not cover a range between 13 and 15 volts, be wary that your alternator could be damaged.

How to Test Alternator (Information Guide)


Now that you’re done testing your alternator turn off the engine and Disconnect your voltage meter and the battery. Close your car hood and take the right action based on the test results.

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