Troubleshoot a 3 way switch

brussoJuly 17, 2011

I have a hall light with two 3 way switches but they have not been wired correctly. You know the drill- one turns on the light, the other one will turn off but then the first one wont turn back on unless the other one is switched, etc. MY question is :what are the steps to determine the travelers and the common ? these are rocker switches.

Thanks again

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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 (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.

    Bookmark   July 17, 2011 at 11:03AM
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Hello brusso

There is always a chance that one or both switches are worn out...and must be replaced..

Assuming that the switches worked previously, and that only the switch terminal connections are wired wrong, I advise the following procedure.
If you are comfortable using a voltmeter or a neon tester. Follow these easy steps (for 2 -3 way switches).

1) Turn the power OFF and physically remove both switches, and take off the wires from the switches only. You do NOT have to remove the GROUND WIRE. This will leave 6 exposed wires (3 in each box).

2) Turn the power ON and identify the HOT wire (it will be the only one of six). Measure between each wire and the metal boxes or GROUND WIRE until you find it.(remember this wire) Then turn power back OFF. Mark this wire

3) The HOT wire found in step 2 is the COMMON wire, and goes on the DARKEST screw of the switch. The other 2 wires can go on either of the two remaining screws. Wire this switch (#1) back up and put it back into the box. This switch (#1) is now correct and you can focus on the other switch. (#2).

4) Turn the power back ON and identify a HOT wire at switch box (#2). Then toggle the (#1) switch and identify another HOT wire at box (#2). The COMMON wire at this switch (#2) box is the wire that was NOT HOT .
(remember this wire) Then turn power back OFF. Mark this wire

5) With the power OFF, wire up the second switch, The COMMON, wire goes on the DARKEST screw of the switch. Then wire up the two HOT wires to the two other screws.

Hope this helps

Let us know how you made out with your wiring project

Have A Nice Day

    Bookmark   July 17, 2011 at 12:15PM
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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.

    Bookmark   July 17, 2011 at 1:09PM
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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!

    Bookmark   April 30, 2012 at 9:32AM
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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

    Bookmark   October 16, 2013 at 8:08AM
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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.

    Bookmark   October 24, 2013 at 12:15PM
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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.

    Bookmark   October 25, 2013 at 6:27AM
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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?

    Bookmark   November 30, 2013 at 9:26AM
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