How To Troubleshoot A 3-Way Light Switch And Most Common Issues

Decora Edge Outlets and Light Switches

A classic electrical troubleshooting project is when your 3 way light switches only work in a certain combination or just don't function as designed. These issues can be tolerated for years but if you want to dig in and solve this issue once and for all let me walk you through an issue at my own home and talk about other common wiring schematics which might help you in your own scenario

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[billk]

I would be willing to bet almost every home owner has discovered after moving in at least one mystery switch! A wiring schematic, even if you draw it, really helps wrap your head around the power routing. Great video.

[lostmagicofdisney]

Thank you. I've been watching 3-way light switch videos all day. I've got myself a 4-way setup. Split level home (built in 70s) with entry light switch at bottom of stairs, at entryway itself, and at top of stairs. I have NO idea what can of worms I'm about to open, but I appreciate these videos. What I have going for me is that all switches work, but I want to update to the Leviton rocker switches.

[hassanbazzi]

I am glad you’re covering this topic. I have updated mine without paying much attention and now I have the same problem. Project for me coming up. Thank you for sharing

[jeffmykytiuk]

You are phenomenal! You have got to be a teacher. Your explanations are simple and understandable. Using a schematic for visualization was perfect. I didn't understand the traveler wire. Now I do. Thank-you. You have a gift, honestly. And actually, I just purchased a 100 year old home which had a ton of 'do-it-yourselfers' living there. I had been begging some tradesman who came to do work to help me with some wiring and the service panel. I am confident I can do it. (The service panel always made me nervous but I understand it after watching your videos.) FYI- I wish you'd make a video for dryer and range hook ups from outlet to service panel. My new appliances require 4 wires; I have three wire outlet. Of course I have tons of questions.

[VladimirYukht]

Thank you Scott for brilliant explanation and for good book you presented. 👍👏

[vg]

If you Google "3-way light switch", there are MANY more ways to do it than in that book. Tens of them. I'm glad yours was an easy fix. Nice one, Scott! You're really busy these days!

Ages ago, at least 40 years, a BIL had disconnected a 3-way light system, but didn't label where the wires went back and he could not figure it out. While visiting one time, he asked me to look at it. I had never done one before, so I had to schematic-it-out on paper to see how it could work, using my electrical experience knowledge, and I also had to figure out how the 3-way switches worked by ohming out where power was being switched and what was normal input, reading one terminal at a time to the other two and flipping the switch. I figured out what is likely the most common way it's done, connected all wires that way and it worked.

About 10 years ago, I wanted my living room light to have two switches. I cut the hole to mount the switch box behind an existing switch on the other side of the wall, added Romex to it from the attic at a junction box, replaced the door switch with a 3-way and added a red 14 AWG runner there, connected it all the same way as before and now there are two switches for the living room. That was a rented house and I left it that way when I bought this house and moved. I may do that to this living room and I'd love to add a hallway light. This house didn't even have a doorbell, so I added one to new Romex in the AC/Furnace closet with the ringer on the wall above the access door.

[offertunatea]

When my family moved to this old house we realized that some of light switches was working weird. I learned how switches works on youtube and figured the problems out and fixed them. It was totally a mess and especially one of those in a multi-gang box with couple of circuits coming in.

[loganebeling]

Hey Scott, love your videos. Do you think you’d make a video about troubleshooting a ceiling fan light fixture combo that won’t work? I’m not sure if it’s the fixture, light switch, etc.

[noreenbaldwin]

It’s like you live at my house- I came to your profile for the screen frame build, and went looking for the screen install video and found this one-I need this too!

[Russianmafia]

You could've kept the original power source and just make the 14/3 a switch loop and use the white wire as your light output

[jeffhansman]

If you could define the term "traveler, " that would help those of us who are new to three-way wiring. My only experience with replacing an old toggle with a rocker switch in this kind of circuit was confusing (and frustrating) as I did not know what all the wires did. The diagrams are helpful, but only if you have some understanding of the function of ALL the wires. Thanks again for your great work!

[Ilikeeminleggings]

I like what you did. Just make sure you don't share neutrals across circuits.

[geoffbooker]

Thanks... I actually have this exact problem in a bedroom. Wish me luck.

[jmcguire]

I'm surprised you didn't switch out those wire nuts for Wagos.

[RCinginSC]

You briefly touched on a scenario that once bit me. While changing a light switch in a 2 gang box, I located the breaker for the light and turned it off. I made the assumption that the breaker turned off power to both switches in the box, (natural assumption) but I was wrong. The 2nd switch was actually on a different breaker and it quickly made me aware of my oversight when I grabbed it. So yes, have multiple switches in the same box on different breakers can and does occur. Be careful.

[asintonic]

Awesome! Good stuff. im learning alot.

[urmastertech]

Darn I could've used this video a few days ago. But I probably will come back to it.

[austing]

Normally, I just follow the flow of electricity, looking at the wiring similar to a water(hot) and drain(neutral) line. The issues are figuring out which wire is which between dust, organization, where your feed and travelers are. For instance, I got an old 20s place that has 4 switches in the kitchen all in the same box, 2 of the switches control the 2 lights above the sink and the main, but then I have 2x 4 way switches right next to each other without any idea what they feed. Then going to the living room that's literally right beside the kitchen, on the wall opposite of the kitchen, there's then another 2x 4 way switches in the corner right beside each other on adjacent walls, ie 2x 1 gang boxes, and it's unknown what those control. Figuring out what's what in situations like so is where the difficulty of electricity comes into play

[markkempton]

Great topic. I moved into a house with a garage with mystery wires in the junction box of a three-way with a dead motion sensor switch. That was literally my first-ever home ownership project. I eventually just made some assumptions and got it working. I've since replaced the new motion sensor wih a Kaza smart 3-way (and added motion sensors elsewhere in the garage), but I still have no idea where all those wires went to.
Maybe I missed it, but how did you conclude what every wire was without tracing them all with a continuity tool or similar process?
Thanks!

[ecarpentry]

I have a three way coming from a switch to the light... kinda confused what to do