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Problem with 3-way switches

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  • Problem with 3-way switches

    Hello All,

    I'm new to this forum, and have a question. I have no formal electrical knowledge/training, but am simply trying to understand a problem I have at my house. I have a back stairwell that appears to be wired with two three way switches, one at the bottom of the stairwell and the other at the top inside wall of the room above. If the downstairs switch is turned "on", the upstairs switch will control the light fixture. If the downstairs switch is "off", the upstairs switch will not control the fixure. I'm stumped. How would I know or tell if the wiring is done incorrectly? I replaced each switch, putting the wires back into the corresponding attachment points. There are three wires attached to each switch. Any advice would be appreciated. The house was built in 1979. Thank you in advance.

    Spakman

  • #2
    Does the downstairs switch work properly with the upstairs switch in the 'on' and 'off' positions? Can you turn the light on and off from downstairs with the upstairs switch in either position

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    • #3
      Originally posted by Spakman
      Hello All,

      I'm new to this forum, and have a question. I have no formal electrical knowledge/training, but am simply trying to understand a problem I have at my house. I have a back stairwell that appears to be wired with two three way switches, one at the bottom of the stairwell and the other at the top inside wall of the room above. If the downstairs switch is turned "on", the upstairs switch will control the light fixture. If the downstairs switch is "off", the upstairs switch will not control the fixure. I'm stumped. How would I know or tell if the wiring is done incorrectly? I replaced each switch, putting the wires back into the corresponding attachment points. There are three wires attached to each switch. Any advice would be appreciated. The house was built in 1979. Thank you in advance.

      Spakman
      You may have a bad switch, check all the conections...be back in a bit.
      "Diplomacy is saying nice dodging until you can find a rock." Will Rogers
      "If a Monkey can do your job, are you in the right profession?

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      • #4
        WBrooks,

        Thanks for the reply. The top switch does not function if the bottom switch is in it's reverse state.

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        • #5
          Polar Sparky,

          All connections are tight. I can't fathom how this could be so screwed up.

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          • #6
            Its wired incorrectly at some point. The two travelers and hot wire are not on the correct terminals on at least one of the switches. You'll need to figure out which is which and correct that. As a usual disclaimer I would not recommend you mess with anything without a good understanding of what you need to do or if you feel uncomfortable with it.

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            • #7
              I appreciate your concern; I will take care to not work on anything hot. How would I go about determining which wire is which? I guess I could identify the incoming hot wire, but don't know which switch it should be attached to.

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              • #8
                Assuming the simplest wiring method, A hot (black) , common(white), ground (bare or green) enter one box, two hots (black & red?) common (white) and ground (bare or green) connect between the two boxes, a hot (black) common (white), and ground (bare or green) exit the second box and connect to the light fixture.

                The switches are designed so that one of the two wires that connect between the two switches is always connected to the hot that enters the first box (single pole double throw switch). Switching the first switch changes which wire is connected to the hot. The second switch (also a spdt) will switch between the two wires, so one way will always connect to a hot.

                The challenge for you is to get the entering hot and exiting fixture wire on the correct screws on the switch. Look for a single dark (brown) screw and two bright (brass) screws. If your switch has these screws, the matching screws will be the terminals that connect between the switches. This assumes no one has removed the screws and reinstalled them in the wrong places.

                This is not the only way to wire a three way switch. sometimes the hot cable and the fixture cable enter the same box. This will change the wiring. If this is the case, the White (and I'm assuming a romex installation) on the three wire cable carries the hot back to the first box and connects to the hot that goes to the fixture. This should be taped at the ends, but may not be.

                Good luck

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                • #9
                  This site will give you a visual of what we are trying to type
                  http://www.electrical-online.com/wiringdiagrams.htm

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                  • #10
                    Nice link, wbrooks.

                    I'm gonna need to lodge a complaint, though. How are electricians going to be respected if one out of three of us can't take a picture without sticking something in our mouths?



                    I've never tasted a bulb to see if it's okay, myself...

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