How Do I Replace a 3-Way Switch? Which Wire Goes Where??

When it comes to a complete house rewire, or even just a simple circuit installation, installing 3-way switching can be difficult for many new electricians (and even some seasoned ones!!) and can be the source of some power issues. In the latest episode of Electrician U, Dustin explains the process so it’s easier to understand.

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So, you are doing a remodel and need to put new devices in. but, low and behold, once you are done, the 3-way that WAS working, is now not working, or is working only when the switch is in one position. What happened? Chances are you got the travelers crossed with either the hot incoming wire or the load wire going to the light. Something that is relatively easy to do and pretty common but is easy to understand once you know how a 3-way switch works.
Let’s discuss first some of the items that are on a 3-way switch and how a 3-way switch works. There are 4 screws on a 3-way switch. A green screw, a black (or bronze) colored screw, and 2 brass-colored screws. The green screw is the grounding screw just like any other device. The black screw is either for the incoming hot (at the box where power is being taken from) or the load wire (at the box where power will be taken up to the fixture/fixtures). The other 2 brass-colored screws are for the travelers that link the switches together and allow power to be applied to a single fixture/fixtures from 2 separate locations. The hinging mechanism is attached (on the inside of the switch. You can’t see it unless you take apart the actual switch!) to the black screw and the other side of that hinge plate is touching the terminals of one of the two brass-colored screws, depending on which way you have actuated the switch. A 3-way switch is sending power constantly to one of those 2 brass screws, it just depends on which direction the switch has been placed in.
So, if you are in a remodel situation, the best way is to put the wires on the screws of the new device EXACTLY as you found them on the original. If the previous electrical contractor properly installed the device and it was working, then you are just replacing the wires on the device one for one. The incoming hot/outgoing switch leg goes on the black screw and the 2 travelers going on the brass ones.
There are a couple of tips that can help. First, unless its absolutely necessary, do not pull any more wires out of the box then you have to. The switch box could potentially be used as a junction box for something else and you don’t want any additional wires in the mix to confuse you. Another super good tip is to look at the sheathing on the cables themselves in the box. The cable that has a single black wire is either the incoming hot or the outgoing switch leg, while the cable that has a black and a red together are going to be your travelers. Especially in a residential installation, be mindful of the bare copper ground wire is not touching any of the other terminal screws or you will end up with a ground fault (and probably a lot of sparks!!) Always turn the power OFF when working on a 3-way switch so you do not get shocked. In addition, make sure the screws are tight on the device and provide the necessary torque with a torquing screwdriver (if the torque values are provided with the device).

[ThomasTomchak]

Finally, I can fix a switch in the basement that I messed up years ago and didn’t know how to fix. Thanks for this video. You’re a great teacher.

[showbizwisconsin]

This is by far the best 3-way switch explanation on YouTube. Great video

[aliviabrewe]

Thank you for thoroughly explaining how the travelers are in the same sheath. Understanding how something works makes it so much easier to remember the process when swapping these out.

[mikeermolovich]

Had to watch a few different videos before this one finally solved my problem. Moved into a new place and the 3 way switches were incorrectly wired. The simple yet crucial explanation of how to figure out which wire goes where when you don't know/forgot where it goes was the key.

[ryanb]

This is one of the best videos to help for this! 3:20-4:00 is key information! Simple and specific. Thank you!

[aleue]

" When you can explain something simply, then you understand it well enough." This was the video that gave me the knowledge that I needed to fix a 3 way in my house. Nicely done, good sir!! I am very happy now. This video gets a like, and I am following your channel. Great job!!

[bobmcdoggish]

Great advice: The two travelers come from the same Romex cable and the single hot or leg comes from another Romex cable.

[RCBInman]

Finally a video that solved our problem! Switching out to all new 3-way Leviton Dimmers and 3-way Leviton switches. Used a no touch voltage tester to test for the hot wire like every other video we watched said to do, only the "hot" wire changed with the position of the other switch, or we had multiple "hot" wires based on the freaking beeping tool. Haha! FIVE frustrating hours later and we finally stumbled on to your video. Why don't the Leviton videos tell you that the travelers come out of the same sheathing? THANK YOU for making this very easy to understand video. Made quick work of the rest of the switches we changed out.

[nadonailer]

Great explanation! 3 way switches always get me. Figuring iut the 2 wires in the same cable are the travellers made sense finally! Thanks

[cmanizzle]

Thank you this helped with my old house where the color of the wires means nothing.

[frankpolizzi]

Thank you for explaining it without a lot of irrelevant information. Your clear instructions with great video makes it much easier for us DIY homeowners.

[robertmassia]

Great video band I finally learned how to tell which one goes on the black and which go on the gold. Because at the house that I bought there is only ground, white, and black. So I have 3 black and 1 white.

[danieltholejr]

Super helpful tips re: the travelers (using the same sheathing - and both going to gold terms) and the "feed" on its own and going to the black term. :)

[jkingmd]

Good video. We have now successfully replaced 45 switches (single, three and four pole) on our first floor. Thanks!

[jerrysuarez]

Finally someone that explains the hot wire and step by step best video for a 3 way switch!

[eutychus]

Appreciate you making this so easy to understand. Simple lesson for my simple mind and I finally got my 3-way working!

[capita]

Love this video! Helps make much more sense diagnosing and troubleshooting for me. Most guides are based on PROPER colors, wire setups, etc. And I’m probably not alone in saying the previous home owner of my house did not do things “Proper”. Keep up the incredible content and spreading knowledge my friend!

[leotexas]

I find that switch loops are the lessons I have to keep refreshing myself with the most of my apprenticeship. 😄

[DominickRuocco]

A great video for homeowners and apprentices. One of the first things I learned was how to properly wire and install a 3-way.

[StrainingDingelberry]

I would love to see some more industrial type videos from you. Motor control stuff would be cool. I don’t think I’ve ever seen you in a plc cabinet or some crazy relay logic stuff.