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4-Way Light Switch

I have two lights in my upstairs hallway. They're controlled by a switch downstairs, a switch outside the master bedroom, and a switch outside a second bedroom.

The switch outside the second bedroom (office) got "stuck" lately, so we bought a four-way switch to replace it. The old one says "4-way switch" on it, so that's what we bought.

There are two black wires and two white wires. I'll call them B1, B2, W1, and W2. They were wired up as follows:

W1   W2
B1   B2


So we wired the second one in that way. It worked when the four-way switch was "on" (the other two lights worked independent of their positions). It didn't work when the four-way switch was off. So I flipped the switch upside down thinking maybe we'd gotten one of them backwards (the wiring remained the same). Same result. Then I tried this:

W1   B2
B1   W2

I flipped the right side, basically. Same result. I'm not 100% sure how 4-way switches work (the "terminal" lights should be three-way switches), but right now it's defying my logic. Either swapping the right side should have worked or it should have caused problems, but not the same problem we saw before.

How can I re-wire the switch so that it works? The four-way switch says "input" on the top and "output" on the bottom, so it's top/bottom and not left/right. Anyone know? The old light switch (the broken one) had no helpful markings on it at all.

7 Responses to "4-Way Light Switch"

  1. I've figured it out. I basically had to install the new switch sideways and then twist it into place (install it horizontally, then twist it to vertical). These diagrams gave me that clue. Thanks Aaron.

  2. You've sorted it now, but basically a light circuit with 2 switches looks like this:

    /o----o\

    live-o< >[light bulb]-

    o----o

    Those are single pole, double throw switches.

    A circuit with more than 2 switches has changeover or crossover switches in between the single pole switches. These look like this:

    -a-o\ /o-c--

    x

    -b-o/ \o-d--

    In one position they connect a to d and b to c. In the other they connect a to c and b to d.

    Circuit with 4 switches:

    /o--o\ /o---o\ /o----o\

    live-o< x x >--[light bulb]

    o--o/ \o---o/ \o----o

  3. I tend to not think of a single light controlled by two switches, as is common on stairways, as ON and OFF, but rather "either/or". That is as long as flipping the current state of the closest switch, flips the state of the light. all is hunky dory. Either switch can be up or down, but flipping the switch will turn the light on or off. Whether the switch is UP or DOWN, or pointing to or displaying ON or OFF is moot; whether the light is on or off, and can be changed by the switch reliably, is what matters.

    Not that you are saying you are concerned with the UP or DOWN aspects of the switch, or whether needless labels of ON or OFF, if they exist on the switch, are being displayed incongruently, but it could possibly be read that way. I think you are more concerned with the circuit effectively reacting to a switch flip action because the included wiring instructions are assuming too much or are too particular about installation in a way that is confounding the actual circuit.

    I have met people that get upset if the wall switch does not equal off, if the switch is flipped down, and there may even be electrical legal code to that effect.

  4. encountered this situation today, what you did, and the way you described it fixed my situation too. thanks a bunch

  5. Hello my Father and I are trying to connect 1 light to four switches. Could you please help with any suggestions to how to connect this contraption????

  6. Erik J. Barzeski

    You figured it out and that is the way I had to wire my 4 way also. Thanks for posting the 'sideways' cure.

    Missy Hill:
    I am no electrician, but as mine is wired (3 switches powering 1 ceiling fan light), there are 2 single pole switches and a third 4 way switch all wired in line to the ceiling fan light (for a total of 3 switches) which will independently turn on the light. Erik pointed out that the new 4 way wired with the common (black wire) wires on the side posts of the 4 way made the switches work independently. My old 4 way had the common wires (black wire) on the opposite posts, (side by side) with the switch in the vertical position. The new 4 way had to be wired with the commons on the same side posts (top and bottom) with the switch in the vertical position. I hope this helps. It confused me for a couple of wiring attempts. I probably should have paid an electrician, but it works perfectly.

  7. you need 2 3-way swiches. the 4-way switch is the middle switch. take out the SPST SWITCHES. NOW YOU ARE HEALED. GO IN PEACE.


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