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I have a light fixture in my house that suddenly stopped working. I tried replacing the lightbulb and still non luck so I decided to try and see if it was the three way light switch itself using a multimeter, but I'm having trouble deciphering the results.

From what I understand, I should be able to:

  1. Turn off power to the circuit
  2. take my multimeter and put it in continuity mode
  3. touch the two screws that are on the same side
  4. when I flip the switch back and forth it should alternate between beeping and not.
  5. The same but beeping for the opposite positions when I touch the screw on the other side of the light switch instead of the screw below

When I perform this test, it beeps regardless of the position when I touch the screws that are on the same side and it doesn't beep at all when I touch the screw on the other side. Does this mean that my switch is broken or am I testing incorrectly? If it is broken, wouldn't the light be on all the time instead of not turning on at all?

Another interesting thing that I noticed - all of the screws on the side of the switch were loose. I went ahead and tightened them up, was that the correct thing to do? What effect could the loose screws have on the light?

Images of the switch below:

enter image description here

enter image description here

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  • That is like a 1 dollar switch, and it's using backstabs instead of the screws. Off to the big-box, might as well throw parts at it...
    – Harper - Reinstate Monica
    Commented May 15, 2017 at 6:03
  • Oh, is it better to wrap the wire around the screws instead of poking through the holes in the back?
    – Brh
    Commented May 16, 2017 at 15:03
  • most of us see it that way rather strongly and take the extra minute to form the hooks. It has the side benefits: it works with any wire not just 14/solid, and it is infinitely reusable, unlike the stabs which are good once. Carefully extract the wires (don't cut and lose length), I pull and twist, the 'release tabs' have never worked for me. Then either strip a bit more insulation and use the screws, or go for the screw-and-clamp type receptacles. More on the issue here. handymanhowto.com/electrical-outlets-side-wire-versus-back-wire
    – Harper - Reinstate Monica
    Commented May 16, 2017 at 16:19
  • For opening the release tabs, I use a 3.5mm slotted screw driver - to release the tension terminal place screw driver in tab and move back or slightly twist to get it to release - works perfectly and easily. Tool As seen here: crum.com/2307041/Product/3.5MM_RED_SLOTTED_SCREWDRIVER I will post this also in my answer just so there is a picture here on stack and also a link.
    – Ken
    Commented Jun 9, 2017 at 20:36

2 Answers 2

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1: You have a 3 way switch which has a traveler line. your odds of having a bad 3 way keeping the fixture from not working while possible would mean that both positions [Off and On] of the switch fail, or both switches have failed. Because when one switch is off the other line is working (either of the switches can turn the light on or off.)

2: Measure for voltage at the fixture wires.

  • Turn one switch On and then Off while measuring do you have any voltage ?
  • Turn the other switch On and then Off while measuring do you have any voltage ?

I am going to post a wiring diagram of a 3 way switch lighting circuit so you can see how and where you need to place your leads when checking the switches. I would be measuring VOLTAGE.

3 Way Switch Light Circuit

There has been a comment on using the push terminals on the electrical switch or using the terminal screws - the push is faster and more likely why people use it and also if you have connected runs. Don't hook two wires on one Screw , use the push terminal to make that additional connection.

As for removing wires from the push terminals: I use a 3.5mm Slotted Screw Driver mine is just like the one pictured below and I have no issues with it - of course I am experienced with push terminals and know that you must insert into the release mechanism and apply pressure on the release either by a slight twist of the screw driver (recommended) or using a prying motion to open the release.

3.5mm Red Slotted Screw Driver

You can obtain the tool from here :

https://www.crum.com/2307041/Product/3.5MM_RED_SLOTTED_SCREWDRIVER

I am not endorsing this vendor, I am posting their link because that is where I obtained the picture from. I have no affiliation with them and have never done business with them.

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Testing the switch in circuit with a continuity tester will show the connected loads. To test it without removing from the circuit the voltage function would be needed with the power on then you would look for 120 across the contacts when the switch is in the off position or in the case of a 3 way the hot will swap from one side to the other. I don't recommend testing with power unless knowledgeable about taking live measurements and there should be someone available to shut off the power and call 911.

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