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How to test the GFCI outlet with a multimeter? October Guide

By shafiq usama

How to test the GFCI outlet with a multimeter

As an electrical engineer, I love explaining how things like circuits and electronics work. I write on my blog to share simple explanations, reviews, and useful tips about the latest technology.

Ensuring electrical safety is paramount in any home or workplace, and a vital component of this is the proper functioning of Ground Fault Circuit Interrupter (GFCI) outlets. These outlets protect against electric shocks and electrical fires by quickly interrupting the circuit when they detect a ground fault. But How to test the GFCI outlet with a multimeter?

To begin, set your multimeter to the AC voltage setting. Next, insert one probe into the smaller slot (hot wire) of the GFCI outlet and the other probe into the larger slot (neutral wire). Ensure the multimeter's probes make good contact. Press the "Test" button on the GFCI outlet to simulate a ground fault. If the GFCI is functioning correctly, the multimeter should read zero voltage. Conversely, if the multimeter shows voltage, it indicates a problem with the GFCI outlet and should be replaced.

Before testing First, you must understand GFCI outlets, how they work, and where you find them.

What are GFCI Outlets?

How to test the GFCI outlet with a multimeter

GFCI outlets, or Ground Fault Circuit Interrupter outlets, are electrical receptacles that protect against electric shocks and electrical fires. They work by continuously monitoring the electrical current flowing through the circuit. If a ground fault is detected, such as when electricity flows through an unintended path (like water or a person), the GFCI outlet swiftly interrupts the circuit, preventing potential harm.

How do GFCI Outlets Provide Protection?

GFCI outlets are equipped with a built-in sensor that constantly monitors the flow of electricity. They can detect even minor imbalances in the current, as low as 5 milliamperes (mA).

When a ground fault occurs, and the current deviates from the usual path, the GFCI outlet reacts within milliseconds, cutting off power and preventing electrical accidents.

Where are GFCI Outlets Typically Found?

GFCI outlets are commonly installed in areas with a higher risk of electrical hazards, such as bathrooms, kitchens, laundry rooms, garages, and outdoor locations. These areas often involve water or moisture, increasing the chances of electrical shocks.

Having GFCI outlets in these locations significantly reduces the risk of injury or property damage due to electrical faults.

The Advantages of GFCI Outlets

The GFCI outlets provide some advantages, including enhanced safety, fast response time, and code compliance. Here these three advantages are discussed:

Enhanced Safety

GFCI outlets provide an extra layer of protection against electrical hazards, making them essential in areas where water and electricity are nearby.

Fast Response Time 

The prompt reaction of GFCI outlets to ground faults ensures that power is swiftly disconnected, minimizing the risk of severe electric shocks.

Code Compliance

In many jurisdictions, electrical codes and regulations are mandated to install GFCI outlets in specific locations to meet safety standards.

Necessary Tools and Equipment Needed

Before knowing how to test the GFCI outlet with a multimeter, firstly, you need to understand the tools and equipment.


To test GFCI outlets accurately, you will need a multimeter, a versatile device that measures electrical properties such as voltage, resistance, and continuity.

A multimeter consists of a display screen, selection dial, probes, and various settings that allow you to obtain precise readings.

Read more about 10 best budget multimeters

Types of Multimeters

There are different types of multimeters available, including analog and digital models. Analog multimeters use a needle to indicate readings, while digital multimeters have a digital display for easy and accurate measurements.

For testing GFCI outlets, a digital multimeter is recommended due to its greater precision and user-friendly features.

How to test the GFCI outlet with a multimeter? Step By Step Guide

Here, guidelines are given to test the GFCI outlet with a multimeter. After reading all the steps, you can successfully test the GFCI outlet with a multimeter. Follow these given steps:

Step #1 Preparing the Multimeter

Start by setting up your multimeter for the specific test. Turn the dial to the "AC Voltage" setting, typically represented by a "V" with a wavy line above it. Ensure that the multimeter is set to the appropriate voltage range for your GFCI outlet.

Step #2 Identifying the GFCI Outlet to be Tested

How to identify GFCI outlet

Locate the GFCI outlet you want to test. Typically, GFCI outlets have two buttons in the center: "Test" and "Reset." Familiarize yourself with the location of these buttons before proceeding.

Step #3 Switching off the Power to the Outlet

Double-check that the power to the GFCI outlet is turned off at the circuit breaker or fuse box. This precaution eliminates the risk of electric shock during the testing process.

Step #4 Testing the Outlet's Voltage

How to test the GFCI outlet with a multimeter

Insert the multimeter's probes into the "Line" and "Neutral" slots of the GFCI outlet. The "Line" and "Neutral" spots are typically labeled on the outlet. Turn on the multimeter and observe the voltage reading on the display. A properly functioning GFCI outlet should show the expected voltage for your electrical system.

Read more about How to test power supply with multimeter

Step#5 Testing the Outlet's Grounding

While still keeping the probes inserted in the "Line" and "Neutral" slots, press the "Test" button on the GFCI outlet. This simulates a ground fault. Observe the multimeter's display for any change in voltage.

Ideally, the GFCI outlet should trip and interrupt the circuit, resulting in a significant drop or complete absence of voltage on the multimeter.

Step #6 Resetting the GFCI Outlet

After testing, press the "Reset" button on the GFCI outlet to restore power. This resets the internal mechanism of the GFCI outlet and prepares it for regular operation.

Precautions and Safety Measures

These safety precautions allow you to test the GFCI with a multimeter quickly. Follow the protection and safety measures: 


Safety should always be the top priority when working with electrical components. Before testing GFCI outlets, it's crucial to understand and follow these precautions to minimize the risk of accidents or injuries.

Shutting off Power

Before conducting any tests, switch off the power to the GFCI outlet you intend to test. Locate the circuit breaker or fuse box, turn off the corresponding circuit breaker, or remove the fuse. This step ensures you won't be exposed to live electrical currents during testing.

Personal Protective Equipment (PPE)

How to test the GFCI outlet with a multimeter

Wearing personal protective equipment (PPE) is essential when working with electricity. Before testing, put on insulated gloves and safety goggles to protect yourself from potential electrical shocks or sparks. This simple precaution can significantly reduce the risk of injury.

Interpreting the Multimeter Readings

Being able to interpret multimeter readings is essential for troubleshooting, maintenance, and ensuring electrical safety.

Voltage Readings and Their Significance

When testing a GFCI outlet with a multimeter, the voltage reading indicates the electrical potential between the "Line" and "Neutral" terminals. A stable voltage reading within the expected range for your electrical system indicates that the GFCI outlet is functioning correctly.

Analyzing Grounding Readings 

During the ground fault simulation, the multimeter's display should show a significant drop or absence of voltage if the GFCI outlet is operating correctly. This signifies that the GFCI outlet detected the ground fault and interrupted the circuit to prevent potential electric shocks.

Common Issues and Troubleshooting Tips 

I will discuss two common issues here, including high voltage reading and no change in voltage. These two issues are given below:

High Voltage Reading

 If the multimeter displays a voltage reading significantly higher than the expected range, it may indicate a wiring issue or a faulty GFCI outlet. Consult a qualified electrician to investigate and resolve the problem.

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No Change in Voltage

If the multimeter reading remains unchanged after pressing the "Test" button, it suggests that the GFCI outlet may be faulty. In such cases, replacing the GFCI outlet is recommended.

How to maintain the GFCI outlet?

After testing, you must take additional tips to maintain the GFCI outlet. Hare some additional information are given which will be helpful for you:

Regular Testing Frequency 

Testing GFCI outlets at least once a month is recommended to ensure their ongoing functionality. Regular testing helps identify any issues promptly and allows for timely repairs or replacements.

Cleaning and Maintaining 

Keep the GFCI outlets clean and free from dust, debris, or moisture. Use a dry cloth or a mild cleaning solution to wipe the surface of the outlets periodically. Avoid using abrasive materials or excessive steam that could damage the outlets.

Replacing Faulty GFCI Outlets and Seeking Professional Help

If you encounter persistent issues or suspect a faulty GFCI outlet, it is best to replace it. Contact a licensed electrician for assistance with the replacement process. Professionals should always perform electrical work to ensure safety and compliance with local regulations.

Final thought on how to test GFCI with a multimeter

To wrap it up, testing your GFCI outlet with a multimeter is like giving it a quick check-up to keep things shockingly safe. Just follow the steps I've covered in this article, and you'll know if your GFCI outlet is rocking' or needs a fixing'. Safety comes first, so use the right gear and be cautious around electricity.

I hope you don’t worry about how to test the GFCI outlet with a multimeter. Regular testing of your GFCI outlets keeps the good vibes flowing and protects you from unwanted sparks. Stay chill, stay safe, and keep those GFCI outlets in check!


Can a GFCI be tested without power?

 A GFCI (Ground Fault Circuit Interrupter) can be tested without power. It has a built-in test button that allows you to check its functionality without electricity. The GFCI simulates a ground fault by pressing the test button and should immediately trip, cutting off power to the connected devices. 

Regularly testing GFCIs, especially in areas where water is present, such as bathrooms and kitchens, is essential to ensure safety. Testing helps verify that the GFCI can effectively detect ground faults, providing crucial protection against electric shock hazards.

What voltage is GFCI?

The voltage of a GFCI, which stands for Ground Fault Circuit Interrupter, typically depends on the electrical system it is installed in. In residential settings, GFCIs are commonly rated at 120 volts, the standard voltage for most household circuits. However, it's important to note that GFCIs can also be ordered for higher voltages, such as 240 volts, commonly found in commercial and industrial applications.

The primary purpose of a GFCI is to monitor the electrical current flowing through a circuit and quickly interrupt the power if it detects a ground fault, providing an added layer of protection against electrical shocks and potential fire hazards.

What happens when a GFCI fails?

When a GFCI (Ground Fault Circuit Interrupter) fails, it can seriously affect electrical safety. A failed GFCI may lose its crucial function: detecting ground faults and promptly interrupting the power supply. This failure can expose individuals to electric shock hazards and increase the risk of electrical fires. 

In a GFCI failure, the connected electrical devices may no longer be protected from ground faults, rendering them vulnerable to malfunctioning and potential damage. Additionally, a failed GFCI can compromise the overall effectiveness of an electrical system, leaving occupants at a higher risk of electrical accidents. 

Regular testing and prompt replacement of failed GFCIs are essential to ensure ongoing protection and maintain a safe electrical environment for residential and commercial spaces. 

What is the disadvantage of GFCI?

While GFCIs (Ground Fault Circuit Interrupters) offer valuable protection against electrical hazards, they have disadvantages. One disadvantage is the possibility of nuisance tripping. GFCIs are susceptible devices that can trip or shut off power even when no ground fault exists. This can occur due to moisture, dust, or minor electrical imbalances.

Another disadvantage is the initial cost of installation. GFCIs are generally more expensive than traditional electrical outlets, which can increase the overall cost when outfitting a building or home with GFCI protection. However, it's important to remember that the long-term benefits of enhanced electrical safety outweigh the initial investment. 

Lastly, GFCIs require regular testing to ensure their proper functioning. A faulty GFCI may provide a false sense of security if not tested periodically, exposing occupants to potential electrical hazards.