Learning, Voltage,

How to Test a Voltage Regulator (Step-by-Step Guide)?

A bad voltage regulator can cause some serious trouble for an electrical circuit. Whether it is common household electrical equipment or a vehicle’s circuit system, keeping the voltage regulator in top condition is vital.

So, let me go through and teach you how to test a voltage regulator.

In general, follow these steps to test the voltage output of a voltage regulator.

  • First, set the multimeter to voltage settings.
  • Then, attach the red lead to the battery’s positive terminal. Attach the black lead on the negative terminal.
  • The multimeter should display a voltage of 12V.
  • Next, turn on the vehicle and check the voltage on the multimeter (13.8V).
  • Finally, accelerate the engine to 1500-2000 RPM and check the voltage (13.8V – 14.5V).

We’ll go into more detail below.

Signs of a Bad Voltage Regulator

Limiting the maximum voltage amount is the main purpose of a voltage regulator. In other words, it will prevent the device or the alternator from overheating or shorting. If your vehicle is dealing with a bad voltage regulator, it might show these signs.

  • Pulsing or dimming lights
  • Displaying unusual high battery voltage
  • Check Engine Light or the Battery Light is ON your vehicle
  • Dead Battery
  • Constant operation failure in electrical components

If the vehicle displays the above signs, it might be time to test the voltage regulator.

Things You Should Know Before Testing the Vehicle’s Voltage Regulator

As you can understand, identifying a bad voltage regulator is important. So, here are some things you should know before starting the testing process.

  • Any car that has an alternator has a voltage regulator.
  • The alternator is designed to keep the battery’s charge.
  • The voltage regulator prevents the alternator from overcharging the battery.

Apart from that, here is the voltage information of a 12V battery. This information will help immensely during the testing process.

StatusExpected Voltage of the Battery
Vehicle is OFF12V
Vehicle is ON13.8V
1500-2000 RPMBetween 13.8V and 14.5V

6 Step Guide – How to Test a Voltage Regulator

For this testing process, you’ll need a digital multimeter and helper.

Step 1 – Set the Multimeter

a man setting up the multimeter at the car hood
Video | ehowauto

First, set the multimeter to DC voltage settings. So, turn the digital multimeter’s dial to the VDC settings. Depending on the type of the multimeter, you might have to change the black and red jack positions. Connect the blackjack to the COM port and the red jack to the V/Ω port.

Step 2 – Connect the Multimeter Leads to the Battery

a man connecting the multimeter leads to the battery
Video | ehowauto

Next, open the vehicle’s hood. Then, connect the multimeter’s red lead to the positive battery terminal. Connect the black lead to the negative battery terminal.

Step 3 – Check the Voltage

checking the multimeter with a voltage reading at 12.55v
Video | ehowauto

Check the multimeter reading. It should be 12V. If the reading is below 12V, you need to replace the battery as soon as possible. Sometimes, the multimeter won’t display any reading at all. That means the battery is dead.

Step 4 – Turn On the Vehicle and Check

multimeter reading at 13.88v
Video | ehowauto

Then, put your vehicle in park and turn the ignition key to the start position. Now check the multimeter reading. The reading should be 13.8V. That means the alternator is properly charging the battery.

Keep in mind: During this step, make sure that the vehicle doesn’t move backward or forward. So, remember to apply the parking brakes.

Step 5 – Hit the 1500-2000 RPM Mark

Now, ask your friend/assistant to slowly increase the RPM value of the engine to 1500-2000. The vehicle should be in a park position during this step.

Step 6 – Check the Multimeter Reading

multimeter reading at 13.95v
Video | ehowauto

The multimeter reading should be between 13.8V and 14.5V. If the voltage drops below 13.8V, that is an indication of a weak battery. If the voltage is above 14.5V, you are dealing with a faulty regulator.

How to Test a Three Terminal Voltage Regulator?

A voltage regulator has three terminals; Input, Output, and Ground. In the above testing process, we observe the battery voltage to detect a faulty regulator. But, here, I’m going to show you how to test the regulator without a battery or an alternator. This kind of method is useful for checking home electrical equipment. (1)

Things You Need

  • 12V power supply
  • LM 7806 regulator (or any other regulator)
  • Digital multimeter

Step 1 – Connect the 12V Power Supply

First, find a 12V power supply and connect its red cable to the input pin of the regulator. Connect the ground cable to the ground pin of the regulator.

Turn on the power supply.

Keep in mind: The red cable carries a voltage of 12V, and the white one has a voltage of 5V. But, here, we only use the 12V cable.

Step 2 – Connect the Multimeter

Then, set the multimeter to the DC voltage setting. After that, place the red lead of the multimeter on the input pin. Place the black lead on the ground pin or the steel plate. The multimeter reading should be close to 12V. (2)

Step 3 – Test the Voltage Output

Now to test the output, place the red lead on the output pin and the black lead on the ground pin. The voltage should be close to 6V.

Tip: When you apply 8-25V DC, the LM 7806 regulator releases 6V DC output.

Wrapping Up

Both of the above testing processes are highly useful for testing voltage regulators. Whether it’s your vehicle or other electrical equipment, remember to check the voltage regulator on a regular basis. It will prevent any unnecessary trouble.

Take a look at some of our related articles below.

(1) testing process – https://www.tutorialspoint.com/software_testing/
(2) steel – https://www.britannica.com/technology/steel

Video References



Shane McRetro

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About Sam Orlovsky

AvatarCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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