How To Test Alternator of Your Truck For Issues

Knowing if your alternator is in good working condition is difficult when you do not know how to determine its health. You can test the health of your alternator using a voltmeter. But you can also try other methods depending on how well you understand your truck. The latest trucks have a computerized charging system which will require different approaches to test for alternators. Shared in this guide is how to test alternator in your truck for issues and know what to do after that.

What you should Know

When using a voltmeter, your engine should rev up to 2000RPM, leaving it running as you test the battery.

A good alternator gives a voltage of between 12.2V to 14.5V, but when the readings on the voltmeter reduce, or it does not make any motion, your alternator is faulty.  

If you are unsure how to test your alternator’s health, take your truck to any auto shop to check the health of your alternator.

Testing the Health of Your Alternator Using a Voltmeter

Consider the following steps to determine the health of your alternator with a voltameter.

Source a Voltmeter

You can ask a friend or buy one if you do not have one. It costs less than $20. Alternatively, you can use a multimeter that measures the voltage and other electrical properties like current resistance. 

Check the battery of your Truck.

For your truck to start, you will need the battery. It is the battery that, in turn, provides the energy necessary to turn the alternator. As the alternator turns, it generates electrical power for your truck’s electric parts, including charging the battery. When your battery is low, you will ot be able to ignite your engine and check the health of your alternator. Consider doing the following to check your battery.

  • Before attaching the voltmeter, turn off your engine.
  • Open the hood or access your battery where it is. 
  • Attach the voltmeter to the terminals of your battery. 
  • Monitor the readings of the voltmeter. If it is 12.2volts and above, then your battery is healthy. 

Start Your Truck and Rev the Engine to 2000RPM

Starting your truck and revving the engine to 2000RPM will draw power from your battery to the alternator. Your engine should be running as you test the alternator. This time, the readings in your alternator should be between 13 and 14.5 volts. Such readings will show that your alternator is in good health. Your alternator is faulty if your voltage doesn’t make any motion or reads figures less than 12 volts.

Turn on the lights, radio, wipers, AC, and all other parts which use electricity in your truck. The voltmeter readings should be above 13 volts to indicate that your alternator is in good condition with other electrical components running.

Monitor Your Alternator

Monitor your alternator gauge while all other electric parts are running, be keen to note if your alternator is straining. If not, it is in good health.


If your alternator is dead, consider buying and installing a new one. You must walk to the nearest shop or make an online order. But it is necessary to buy an alternator from a shop so that they test it in your presence.

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