How to test a Light switch with a Multimeter – Meterreviews

Light switches are the most important equipment to get control over power supply running to some electric apparatus like fans, bulbs, leds, or some other electric items. Sometimes we experience a sudden outage of bulb or fan even when the button was on. In that case, there are two possible scenarios, either light switch has stopped working or fan or bulb blown out (having some issue). For concluding this you must know “how to test a light switch with a multimeter”. After this test one can finalize the real issue behind power failure.

For testing light switches you must know the correct way to use a standard home use digital multimeter for basic level tasks. Doing a DIY self test on live wires may be dangerous for newbies, so make sure you have enough knowledge about working on live power supply and multimeters safety requirements. We tried to make it simple so you, so we are giving some easy steps below by which you can test a light switch for power easily.

Tools and accessories needed for testing a wall switch

For this simple test required tools are a noncontact voltage tester( if you don’t have one you may also use a tester), a multimeter, screwdriver, cutter, and safety gloves. Follow the steps given below,

How to troubleshoot a light switch

A light switch works on a simple mechanism of open and short contacts. A short contact means power supply is allowed to pass through this point, while an open contact will cut the power supply path which means no power to bulb or fans. Now our main purpose is to check if light switch contacts are working properly, wires are fine, and have an intact connection with switch terminals. Voltage level is also an important factor, check whether it’s in normal range or not.

  1. First step for fixing a light switch is to power off the circuit breaker which is supplying power to the faulty light switch in order to do safety masures before test.
  2. Remove light switch cover with help of screw driver, take it out carefully.
  3. Now check voltage presence in its wires through a non contact voltage tester, if you don’t have one a general tester could also be used for this purpose. Make sure there is no voltage presence in light switch circuit.
  4. Disconnect all switch wires and pull out light switch for further examinations.
  5. Don’t forget to mark wires with respect to terminals they were connected to, you may use tape for it.
  6. Now set your multimeter on continuity with audio beeper option.

Light switch types

There are usually two types of light switches, one is single pole and other is three pole or three way switch. You have to identify first which type of switch you are working on. If switch has two terminals then it’s a single pole terminal, if it has three terminals then it’s a three pole light switch. In the case of three way switch, don’t forget to mark the wire which is connected to the dark terminal. It will help you in accurate re connection of wires after test process.

How to test a single pole Light switch

  1. Connect multimeter both leads to light swicth terminals when switch is at off state.
  2. Multimeter should not detect continuity in off state, if you are testing it in ohms reading should be 1 or more which means there is no continuity.
  3. Now switch on the light switch and observe changing on multimeter screen.
  4. At on state meter will will produce beep sound as indication of continuity presence.
  5. You’ll get an ohm reading near to zero for confirmation of valid connection.
  6. If you are not getting these results, replace your light switch immediately.

How to test a three way Light switch

Procedure of testing a three pole light switch is almost same as single pole. In three way, you have to make dark terminal a common one and test it with the other two terminals by making connections one by one. Other parameters are same as above, like when switch is at on position a near to zero ohm reading or a beeper sound will be an indication of true light switch functionality. At off state switch should give 1 ohm reading or no beep sound will be produced by multimeter if you have a meter with continuity beeper feature.

Finalizing the task

Once you have done testing the light switch and found it fine, you should mount it back properly by reconnecting wires in true manner( that’s why we told you to mark down wires when disconnecting them in order to re connect them accurately after the job). Moreover, put the wires in box carefully and tighten screws.


Sometimes a minor issue can lead to a bigger problem, in this case, a loose wire connection can cause light switch failure. In that case only re connecting the wires rightfully can solve the problem. We hope this guide article will help you identify issues with light switches and solving them with fewer efforts. We will advise you again here to get little knowledge about how to use multimeters and electrical safety practices before doing any test by yourself.

In fact if you can use a dmm efficiently, you don’t need to call electricians for minor faults at home or office. Just follow the steps which are given above correctly, if you still have confusion watch this guide video.

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