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

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.

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.

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

I love troubleshooting 3-ways.

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.

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.

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!

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.

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.

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

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!

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

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

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.

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

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!

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

Definitely agree on the B&D Wiring book. Was my go to when I worked at Menards for explaining how to wire three way switches. Working around my house, I always mark the common wire with a piece of electrical tape before I disconnect the old switch so I do not make any mistakes putting the new switch in. I usually use blue or orange as these colors are seldom used in home wiring. I've replaced at least three pairs over the years (20 years, 2 houses) and have yet to have problems afterward. Watching your video, I cringed at the old three way switch #1. Who the heck wired that with so much exposed copper past the screw?

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

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

The nice thing about physical reference books for electrical work is that they don't need electricity.

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

More or less as an aside, I have run into a situation where the switches were after the light, switching the neutral. While this works, it is not code because it leaves a socket hot with the switch off. It can happen especially in older homes which were remodeled from knob & tube and the wires were not properly identified.

Unfortunately in my case one of the 3 way switch box in my hallway is missing a hot wire. it only has 1 red and one black and a neutral. Which is the reason i'm having this issue

Any time I was ever ask to work on a three or four way light switch I always ask to simple questions. Has it ever worked? Has anyone else tried to fix it. I have found this saves a lot of time trying to undo someone else's mess. If the answer to both questions is yes, you may as well totally unwire every thing and start from scratch.

We had some weird 3-way switches that the previous owner had installed. I ended up replacing all switches with decora, which let me see what he did wrong. In part, he had installed dimmers that weren't 3-way in a few spots. It was a couple of years ago, so I don't remember details any more.. When I was relacing switches, the starting point is to do a 'head-count' of switches before heading out to the store How many 2-way switches do I need? How many 3-way switches? I even had a few 4-way switches. I got to the point where just by removing the faceplate, I could identify which switch was what type.

4 way is pretty easy to understand but it might be worth doing a video.

Awesome! Good stuff. im learning alot.

I don't know why you threw out the old switches. Kind of unneeded added cost

I had that problem in this house, in the kitchen light. 3 way dimmer switches. Naturally the idiot that had this house before me did it all wrong. I had to not only replace the switches but when I opened it up, I found a plastic box. Well that absolutely HAD to come out so I took it out and replaced it with a steel box. I carefully threaded all the wires in and clamped them down... Not sure what they did to the clamps but these days, you clamp them down and it pierces the Romex and creates a short. That was "FUN" (Sarcasm) So anyway, I got that corrected, did a new home run, and replaced the dimmer with regular 3 way switches and wired them PROPERLY. Also grounded, except for the fixture. Not only was this house wired without grounds, the idiot before me didn't believe in using grounds, and cut them off when he used new wire. On top of that, the house failed inspection when he tried to sell it, and instead of putting a sticker on the lavatory GFCI that reads "No Ground" he decided to bootleg ground it with neutral to ground, creating a VERY dangerous situation. What's more, there was a ground wire there, in the wall, and he ignored it. A total schmuck he was. I would have sued him if I got a worse shock than what I got. I wish people would just do things right or leave it alone, and for the love of DOG, GET RID OF THESE PLASTIC BOXES ONCE AND FOR ALL !

I am trying to wire in some new switches in my daughter mobile home and you know they have those weird press in switches for the lights and for some reason when I cut the wires and wire them back together, I have to turn on my ceiling fan for the porch light to work. It’s 2 switches in one box, one for the ceiling, fan and one for the porch light. Any help would greatly appreciate it. I really enjoy your channel. Keep up the good work.

This is why I cover outlets with tape before spraying.

You should ask Santa Claus to bring you a cordless drill to use for all that screwing taking off the plates, etc

That may have Mia wired from the build because you can tell all the wires had white paint where the painted the house on the rough in

Thanks for the video. It looks like the switches were initially installed incorrectly. Did this ever work?

आमच्या भारतामध्ये 2 वे स्विच म्हणतात. मी एक इलेक्ट्रिशन आहे मी हे सर्व काम करतो. #TechnicianDnyaneshwar

We call this 2 way switching in the UK. 2 switches, so 2 way.

I hate romex so bad, ive worked with emt all my life and it makes wiring all this so much easier since you just pass travelers into another pipe and leave a tiny loop, giving you so much more room, and no need to wirenut

And I'm try to fix my friends DOUBLE rocker switch where only one switch is the 3 way...😕...ayyiyiyiyiyi..... (second try coming in a few days...) ( I might need to call you for HELP !! )

I wonder if that book has a "3-way light switch with pilot" diagram. I wired one of those a while ago, it's a doozy.

nous en France on se fait moins chier ,on utilise un télérupteur ...

3 way switches are very confusing.

Am I the only one that noticed a red wire tied into the neutrals?

This has nothing to do with the video, but rather, the name of 3 way switches. Why is it called a 3 way switch? The only thing about it that’s three is the fact that there’s 3 terminals for the current carrying conductors. 2 way switch would make so much more sense.

Jesus Christ, warn people to turn off the power before poking into wiring.

🤗💚💚💚

Link to the book is broken and it was a pain in the ... to find.

A guy that has to use a book to fix a wiring problem is teaching others??