The travellers will pass in the same cable the common may or may not depending on the way things are wired up, but if the common does feed back through the same cable as the travellers it won't be connected to the switch on the other end (should be a hint).

As you have surmised, most likely someone wired the common terminal of the switch to one of the travellers. The first step is to identify that terminal on the swtich (most likely they replaced an existing switch and assumed the screws were all in the same place on both). Once you've identified the common you usually will find symetry in the wiring on the travellers to figure out which should be connected.

Well, thanks to both of you. I found the travelers were in the same cable then followed the steps from linesman. It's all done!!. BTW, this light and switch were not working correctly for at least 7 years. My wife gets back from her trip on tuesday and will be very surprised. Thanks again.

OMG! I have now wasted literally almost 2 1/2 days trying to figure this out. Bought an older home & it has some "challenging" wiring...All I wanted was to connect a 3 way switch properly...who knows how long it was wired using an old trick that will make them work using single pole switches...but not right & not to mention, they had bypassed the ground wires. Everything I read online just kept saying to find my "common" wire (which in my past experience always meant "hot"). They all refer to "tagging" the hot wire, but that didn't happen so I just found the black wire that was "hot"!

Thank you for finally explaining that for the second switch of a 3 way...It's the not "hot" that is common! I know I should have thought about that...but my question is..."When explaining wiring to a DIY'er...why would anyone assume that we knew this already?"

I am so glad I found this forum. Thanks again for saving my sanity!

I am attempting to troubleshoot the following: two 3 way switches operating one light:First i closed breaker then i disconnected all wires from switches(there were 3 at each switch). Then i opened the breaker and found the hot wire at switch #1. At switch #1 i connected hot to common terminal and the remaining wires to remaining terminals.
Now i proceeded to switch #2 and with the breaker still on i tested those wires for power and found that one of the 3 wires was hot (lets call that wire 2-A) i then proceeded to flip the switch at switch #1 and retested all the wires at switch #2 for power. I found that 2-A was no longer hot but the remaining wires were hot. Does this test at switch #2 successfully identify the common wire? Also is the hot lead that goes directly to the light fixture located in the same box containing switch #2

Ok i have tried the above steps and in my case the power comes from the light to the switches, and for some reason when everything is disconnected I have two hot wires (one in each box).
Each box contains one black, one white and one red. Both blacks are hot. How is this possible and what do I do about it? Every diagram I have looked at (that shows the power to the light) if everything is disconnected I should only have one hot.

Make sure that the power at the light is made up correctly, and if it is then you may have one or more 4 way switches in the arrangement that you don't know about.

I've got a problem with a light that has two 3 way rocker switches as well. One switch has a black and red in the same sheathing and then a red that comes from a separate sheething. The other switch has a red white and black that are all in the same sheathing. When I disconnected them all and tested I had 5 "hot" wires of the six. I'm quite confused. anyone able to help with this?

Your explanation of how to fix the 3 way switch was perfect and simple. Thank you. Just out of curiosity would that have worked if my 3 wire did not run from switch to switch? Thanks again

Mark

Thank you so much for posting this, linesman. My 3 way switch has not worked properly for 11+ years. I decided to tackle it today after finding your directions. It WORKS! Thank you so much!!!

Dave

God Bless you Linesman! My house was built by an electrical contractor who used many unusual techniques in its construction, much of which was of course in the electrical. Two years ago a three-way switch for the basement stairwell went out and I tried to replace it. For the benefit of those who thought they were following your directions (like me at first), I had been trying to trace my hot wires with a non-contact voltage detector. The switch at the bottom of the stairs was in a box with three others. The detector would buzz no matter where I stretched the bare wires so I finally got smart enough to drag out my good old analog multi-meter and sure enough all the wires showed a small amount of current except of course the COMMON on the live end which registered 110v. Duh! I then followed your directions and like one of your other readers who messed with his for two days, I finally wired the two switches so that you can turn the light on and off from both ends. My daughter's family is living in my basement and I can now rest assured nobody is going to fall down the stairs in the dark. I can't thank you enough and I hope you tune in and read this.

Thank you Linesman! I re-installed both my 3-way switches twice before finding your clear instructions. Part of my previous mistakes were in using a voltage sensor instead of a voltmeter to identify the HOT wire. After properly identifying that wire (I thought it was in the other box) the rest was easy, following your directions.

OK Well that didn't work. After following the directions of linesman, I don't have ANY power to my ceiling fan/light ????? Trying again but I double checked every move the first time...

I would guess that because it is a paddle fan and light, the wiring will look something like this. Except that there is probably an extra wire going up to the fan so that the fan and light can be controlled separately.

If you can take a picture, or describe what wires you have, then I could draw you a diagram.

checked with multi-tester. rewired.now I have control from either one switch OR the other, but not from both ends...

I hope you did not take any wires with wire nuts apart. Quit guessing, and take the time to explain what you have here in detail. It is not that hard to figure out unless you are trying to do it by linesman's directions and don't know which switch is #1 or #2. If you don't know which switch is which, and try to take a shortcut, a meter will just lead you the wrong direction. You should not need a meter unless you took wires apart that you were not supposed to, and royally messed it up. I have never needed one in 30 years of being an electrician.

I have the same situation with a hall light with switch A (rocker) at the bottom of the stairs and switch B (toggle) at the top of the stairs. The second 3 way switch (switch C) next to switch A was messed up by a kitchen remodeling contractor (who moved the other end (switch D) a foot from the original spot). An electrician friend helped fix that (had to open the wall above the switch D).

Now switch A was originally a toggle switch and all worked fine. Then a handyman installed a rocker and ended up doing something wrong. He tried to fix the issue but failed. I am following lineman's instructions. 5 of the 6 wires are hot using a GB voltage sensor with 1 non-hot on Switch B only. I hate to call on the same friend again. I suspect the issue is with switch A but not sure. See photos below. Advice please?

This is switch A. Blue, red and black. All test as hot.

This is also switch A and I am wondering if the black wire should be in the hole next to it with the push slot. The blue and red were in the holes next to the push slots.

This is switch B. 2 black 1 red (no blue???). 1 of the blacks and the red test hot. 1 non-hot black.

It looks like both switches are wired wrong, but I can not see the whole picture from the pictures.

Your travelers are black and red. That means the blue wire goes to the common (black screw). On the switch with two black wires, the travelers are the black and red that come out of the same cable. The "other" black wire goes to the common (black or odd colored screw)

Unless someone rewired the connections wrong in the back of the box, it should work properly then.

" I am wondering if the black wire should be in the hole next to it with the push slot"

The "push slot" will only accept #14 wire. All holes lead to the same connection, so it does not matter which hole you use as long as it is associated with the same connection.

Thanks you were right on both switches. The blue should have gone to the common/black screw. Switch A was the only one that the handyman messed with (I think). Also, I think the voltage sensor I was using wasn't the right tool to use. I fumbled around with a multimeter (never used one) that I was able to borrow and I managed to figure out that the blue was the hot one. The rest was easy. Thanks again to all.

I feel like I have lost my mind with the two 3 way switches in the stairwell. Switch A is a dimmer with 1 black and two red on the switch. In the box, there is a black, attached to two other blacks. One red and one black which go out the bottom. Switch B has a red attached to common, and two blacks as travelers. I cannot wire Switch A so that Switch B will work if Switch A is off. Switch B only works if Switch A is on. Please help! Thank you

"Switch A is a dimmer with 1 black and two red on the switch."

On a standard 3-way, the odd colored one (red in this case) is the COMMON. The two blacks are travelers.

"In the box, there is a black, attached to two other blacks."

This is the COMMON that attaches to the red wire on the switch.

"One red and one black which go out the bottom."

These two wires are in the SAME cable or conduit, and are the travelers. One attaches to each of the two black wires from the switch. One will be black-black, and the other black-red.

"Switch B has a red attached to common, and two blacks as travelers."

This is WRONG, because the travelers are the black and red pair that come out of the same cable or conduit. The black wire that comes from a cable or conduit with just a white wire and no red wire is the common.

Of course, there are plenty of ways to run wire that can add other red or black wires to make this more confusing, but the basics still apply. And, sometimes conduit can have all the wires in the same raceway, making it a different color scheme, or trickier to distinguish.

Thank you so very much. I wired the toggle same as it was before and had the red as common instead of black. You are fantastic and I so appreciate your quick response! Thanks again!

Ron Natalie:
"The travellers will pass in the same cable; the common may or may not
depending on the way things are wired up, but if the common does feed
back through the same cable as the travellers it won't be connected to
the switch on the other end"

Thank you, Ron! All of the other answers I was able to find required a voltage tester (which I can't acquire at midnight) and your answer simply required some logic and process of elimination. Before using your advice, I spent at least 2 hours blindly trying to figure out what's what by repeatedly switching wires around (unsuccessfully).

Instead, all I had to do was find which one of the switches had two wires coming from a single Romex bundle and the third wire coming from a different bundle. The other switch had all its wires in a single bundle. This told me that the two bundled wires on the first switch must be the Travelers, and the third wire (the odd-man-out) must be the Hot wire.

So I simply attached the Hot wire to the black screw on the first switch, and attached the other two wires to the silver screws on both switches (identifying them at the second switch by their colors from the first switch). That left me with one remaining wire in the second switch box, which toId me it must be the common wire. I attached that to the black screw on the second switch and now everything works correctly!

Omg!! Mr Linesman, you are the best!! After wasting 2 days trying all kinds of wire combinations, and just about to give up, I found your post, followed your directions and it in 20 minutes it all worked correctly!!! Thank you!! Thank you!! Nobody online explained that the common line is not the hot one on switch 2! Life saver!

Thank goodness for Mr Linesman's post. I'm having a similar issue in my house with multiple switches and I will be trying this tomorrow!!

Funny, in my 27 years of being a licensed electrician, I have rarely needed to use a tester to determine which wires are the travelers. (Maybe a handful of times in extreme situations where some handyman has switched wires around in a light box) It is just the long and complicated substitute for looking in the boxes and seeing which wires go together... kind of like Columbus going west to reach the east.

"It is just the long and complicated substitute for looking in the boxes and seeing which wires go together..."
So, pretty much how the first commenter explained it (Ron Natalie).

@linesman - thank you so much! You just saved me an electrician visit. If you lived nearby, I’d buy you a beer! Not only did you provide crystal clear instructions to solve the problem, but I think I finally actually understand how 3-way switches work. LOL I appreciate you!

I've been spending days trying to change the 3 way switch to 3 way smart switch. I've already identified the line in box A and the load in box B. attached it to the common terminals in each box. When putting back on the dumb switches, no problem. Works like it always has. When putting on the smart switches, the light stays on and there's no power coming from source/line to box A or any of the wires in box B either, obviously. light just stays on and the switches do nothing. The only thing i can think of is, in box A, can't figure out why the white wire, in the 3 wire bundle with the 2 travelers, was the load in box B, but in box A, it is twisted with all the neutral wires. Then also in box A, what i expect would be the neutral (the white wire that came in the bundle with the black line wire) is nutted together with the line in from a different bundle for a different switch in the same two gang wall box. I'm almost a 100% sure it was like this the whole time before I even messed with it (however I did have a neighbor try to help and he rearranged a few things that I thought completely reversed). Also keep in mind that when I wire it back up the the dumb switches, it works fine.

Some one please help. Photos attached.

No photos! For a dumb 3-way to work, you need a source wire (usually black) going to one switch, two travelers (usually black and red) going between the switches, and a load (may be either black or red) going to the light; this is the simplest and most basic system. Neutral and ground wires are not necessary for this to work, although code probably requires the ground (green wire) to be connected. Smart switches may also need the neutral (white) wire connected.

I'll try to upload the photos again but anyways, i figured it out. After reading this blog about white wire connected to black hot and another black, i realized my neighbor had messed me up when he took all the white and joined them because he was adamant that white should always be neutral. I thought i had reversed the mess that he made based on a photo i took before he came over but it wasn't a great photo so it was hard to see which wire was originally going where.

https://diy.stackexchange.com/questions/153596/why-neutral-wire-connected-to-load-wire

This blog made sense of it all and after staring at a close up of all the wires, i realized how it was supposed to have originally been set up. i switched around two white wires and now it works perfect. The line wire to box B was white and was still joined with all the neural wire after my neighbor came over to try to help. I thought i out it back there way it was supposed to be but instead i had a neutral wire joined with the hot black wire from power source. Switched the two back to the way they were, and it's finally all good.

Oops. That's yellow writing that says "neutral bundled with line 1" is supposed to say... Connected to "Line 2"

Turned out the white wire was line to box B instead of load but for some reason when all the white were still bundled together and i tested all the wires with voltmeter, it seemed to be all reversed.

Thanks for this write up, I spent hours trying to fix one switch upstairs and did not know what I did to get it to work. With your writeup I found that the common is not the one with power on the second switch. I was given bad advice before.

Now I can do a switch in about 5 minutes. Thanks. Finished all the switches downstairs today.

Thank you linesman for the writeup. Worked perfectly!

Years later, this post still saves the day. thank you.