How to Test a Light Switch with a Multimeter (7-Step Guide)

People use their light switches thousands of times every year. It’s natural for them to wear out or deteriorate over time. There’s no need to be worried if you believe you have a faulty light switch.

You have the option of calling an electrician or testing the switch yourself. I’ll teach you the latter.

In general, to test a light switch with a multimeter, follow these steps:

  • Set the multimeter’s dial to read ohms. You’ll see this with a K and Ω symbol.
  • You can set the dial to 100 ohms if your multimeter doesn’t have auto-ranging. Plug the black lead into the negative socket, while the red one should be in the positive one.
  • Touch the meter leads to the switch’s terminals.
  • The multimeter should indicate a near 1 ohm only when you toggle the switch off, while when you switch it on, it should measure an average of 10 ohms in the multimeter. If you are not getting the same results, it’s a sign that you have a faulty light switch.

Fortunately, checking a light switch is simple if you have the right tools.

Tools You Need

multimeter and tools

The following is what you will need:

  • Non-contact voltage tester
  • Screwdrivers
  • A multimeter
  • Electrical tape

Step #1: Turn Off The Power

female finger switches the lights off

Turn off the correct circuit breaker in your home’s main distribution panel to turn off the electricity to the light switch circuit. If you live in an old-fashioned residence with a fuse panel, completely detach the corresponding fuse from its socket.

Always verify the power connections before detaching the wires and unplugging the switch because the service panel index or circuit labels are frequently mislabeled.

Step #2: Test the Power


Loosen the switch cover plate bolts and lift the cover plate off to reveal the switch wire. Use a non-contact voltage tester to examine each wire in the electrical panel without touching them.

Additionally, examine each switch’s side terminals by touching them with the tester’s tip. Proceed to the service panel and switch off the appropriate breaker if the meter detects any voltage (lights up or buzzes), then repeat until no voltage is detected.

Step #3: Recognize the Switch Type

Types of switches include:

  1. Single-pole switch
  2. Three-way switch
  3. Four-way switch
  4. Dimmer switch
  5. Occupancy sensor switch
  6. Smart Switch

The fact that switches come in various types is a point to consider when evaluating them. This is why we must first determine which type we are dealing with.

There are a few ways to determine which type of light switch you have:

  1. Look at the switch itself: The switch should have markings or labels indicating its type, such as “single-pole,” “three-way,” or “dimmer.”
  2. Count the number of wires: Single-pole switches have two wires, while three-way and four-way switches have three. Dimmer switches may have additional wires, depending on the type.
  3. Test the switch: You can test it to see how it functions. For example, a single-pole switch will only control a light or other electrical device from one location, while a three-way switch will allow you to turn the light on or off from two locations.

Step #4: Unplug and Detach the Switch

Remove the wires by loosening the terminals’ screws. These will bring the switch to a stop.

Put the switch on your work surface to test it. Before removing your light switches, you might want to clean them.

Step #5: Perform a Continuity Test on the Switch


You will need a continuity tester to do this. Luckily, this is also possible using a multimeter. 

Continuity testing differs depending on the switch type. That’s why we’ve divided them into categories and described each one separately:

Single-Pole Switch

light switch

First, take the tester and connect one of the wires to a terminal. Get the probe and attach it to the other terminal. To light up the tester, flip on the switch.

If it lights up, it signifies the switch is in good shape and is functioning properly. The contrary indicates that the switch has failed. Replace the light switch if this occurs.

Three-Way Switch

Connect the black wire of the continuity tester to the com terminal. This section is identical to the previous one. After that, connect the probe to a traveler terminal. To measure the voltage, you should use a multimeter.

Inspect to see if the light comes on when you turn on the switch. Test the other terminal if it does. It isn’t accurate if both of them don’t light up. Detach the run-down switch and replace it with a new one.

Four-Way Switch

These switches have four terminals. It can be puzzling at times, but it isn’t overly complicated. All you require is a small amount of attention.

Attach the testing wire to the attached dark terminal first. It would be best to connect the other wire to a light-screwed terminal. Flip the switch on and off.

For one position, you will have continuity. If you see both or none, it may not be very accurate. Connect to the other terminals and repeat the process when you’re finished.

You should detect continuity in the opposite position this time. If this does not occur, the switch is most likely defective. If you obtain a different reading, replace the switch.

Step #6: Replace or Reattach the Switch

Connect the circuit wires to the switch. Fasten all screw terminals and ground screws tightly after that.

If you’re replacing the switch, follow the same steps. Simply ensure that the amperage and voltage are equal. When you’re finished, return everything to its original location.

Step #7: Finish the Job

light switch diagram

Reinstall the switch, insert the wires neatly into the electrical box, and fasten the switch strap to the electrical box with its mounting bolts or screws. Reattach the cover plate. 

After reinstalling the fuse or resetting the circuit breaker, restore power to the circuit. Verify to see if the switch is working properly. (2)

Common Switch Types:

  1. Single-pole switch: This is the most common type of light switch. It controls a light or other electrical device from a single location, such as a wall switch in a room.
  2. Three-way switch: This switch is used in a circuit with two light fixtures controlled by two switches. It allows you to turn the light on or off from either switch.
  3. Four-way switch: This switch is used in a circuit with three or more light fixtures controlled by three or more switches. It allows you to turn the light on or off from any of the switches in the circuit.
  4. Dimmer switch: This type of switch allows you to adjust the brightness of a light fixture by turning the switch up or down. It is commonly used in living rooms and bedrooms.
  5. Timer switch: This switch is programmed to turn a light or other electrical device on or off at specific times. It can be used to automate lighting in a home or office.
  6. Occupancy sensor switch: This switch turns a light on when it detects motion in a room and turns it off when there is no longer any motion. It is commonly used in public restrooms, stairwells, and other areas where lights may be left on unnecessarily.
  7. Remote control switch: This switch allows you to turn a light on or off using a remote control. It can be convenient for hard-to-reach switches or for controlling multiple lights at once.
  8. Smart switch: This type of switch can be controlled remotely using a smartphone app or voice assistants such as Google Assistant or Amazon Alexa. It can also be programmed to turn lights on or off at specific times or based on other triggers, such as the sunrise or sunset.

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About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gCertifications: 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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