How to Test an Alternator – How to Test an Alternator with a Voltmeter

Do you want to learn how to test an alternator? If yes, this article is for you. You would be educated on how to test an alternator with and without a multimeter, how to test an alternator with a voltmeter, and lots more. So, kindly read through to the end.

How to Test an Alternator
How to Test an Alternator

How to Test an Alternator

The parts, components and accessories of a car are so many that it may be quite difficult taking note of them all. However, the Alternator is a necessary automotive part that you should not neglect.

So, what is an Alternator and what does an Alternator do? The Alternator is an automobile part that converts the mechanical energy of your car into electrical energy.

The function of an Alternator in a car is to charge the battery and provide power for the electrical accessories.  All these happen while the engine of the car runs. Electrical accessories in your car include; the headlamps, radio, Air conditioner etc.

How to Test an Alternator with a Multimeter

A bad alternator may lead to more damage in the car. But how do you know if your alternator is faulty? You can do this by testing the alternator with a multimeter. A multimeter is an electrical device that is used to test electrical connections and also measure voltage.

Don’t know how to test an alternator with a multimeter? This article has got you covered. Follow the guide below to check if your alternator is bad with a multimeter:

  • Locate the Alternator on your car. You can do this using the manufacturer’s manual.
  • Set the multimeter to a DC volt (above 15 volts).
  • Place the negative terminal of your battery on the black cable of the multimeter.
  • Connect the red cable of your multimeter to the positive terminal of the battery.
  • Start the car and let it run while taking note of the reading on the multimeter.
  • The normal voltage reading should be between 14.2-14.8 volts.
  • Turn on the electrical accessories and take note of the voltage.
  • If the voltage drops below 13 Volts, your alternator may be bad.
  • Switch off the engine and observe the voltage reading on the multimeter.
  • A voltage reading below 12.6 volts indicates a bad alternator.

If your alternator is bad, you should book an appointment for an alternator replacement. You should also note that the method of testing your alternator by letting the car run and loosening the negative terminal of the battery is very risky.

This method may cause serious burns to the alternator, electrical components and voltage regulator.

How to Test an Alternator with a Voltmeter

Alternatively, you can use a voltmeter to check the status of your alternator. A voltmeter is a device which is used to measure the electrical potential difference between two points. It is an alternative to the multimeter.

Don’t have want to use a multimeter to check your alternator? If yes, you should follow the steps outlined below:

  • Park the car and switch off the engine.
  • Open the bonnet (hood) of your car.
  • Locate the car battery with the owner’s repair manual.
  • Connect the voltmeter to the battery. Do this by placing the red lead of the voltmeter to the positive terminal of your battery and the black lead of the voltmeter to the positive terminal.
  • Make sure your skin does not come in contact with the battery.
  • Read the voltmeter and if it is above 12.2 volts, you can use it to test the alternator.
  • If the voltmeter reads below 12.12 volts, you would need to charge the battery as you would not be able to use it for the alternator testing.
  • Start the engine and let it run at a high revolution per minute.
  • Check if the voltage readings have increased.
  • If the voltage reading is between 13 volts to 14.5 volts, chances are that your alternator is still in good shape.
  • If the voltage reading reduces, your alternator is probably bad.
  • Repeat this process with the headlamps, Air Conditioner and radio on.
  • When the voltage still increases with these electrical components on, your alternator is still in a good shape.
  • If otherwise, your alternator is bad and may need a replacement.

With this, you would be able to test your vehicle’s alternator with the voltmeter.

How to Test an Alternator without a Multimeter

Don’t have a multimeter or voltmeter? You can also check the status of your alternator without having to use any of these electrical devices. However, this may not be a reliable method.

To test an alternator without a multimeter, the steps outlined below would help you:

  • Check the dashboard on your vehicle for an Alternator gauge.
  • If there is an alternator gauge, turn on the engine with your eyes fixed on the alternator gauge.
  • Take note of the voltage reading.
  • Put on the Air conditioner, radio, head lamps and other electrical accessories on your car.
  • Run the vehicle at a higher revolution per minute.
  • If the voltage increases when the engine runs, your alternator is working fine.
  • Go to the bonnet of the car and listen for any unusual sound while the engine runs. An unusual sound which increases while the electrical accessories are turned on indicates that the alternator is bad.

With the steps above, you would be able to tell if your alternator is bad. The alternator is a key component of your vehicle. To prevent your car from stalling on the road and you getting stranded, you should replace a faulty alternator once you notice it is.



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