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Thread: 3 way switch.. I'm puzzled

  1. #1

    Default 3 way switch.. I'm puzzled

    I'm not an electrician, my friend is and he is puzzled as well....

    At my mom's house there is (what should be) a three way switch controlling a light fixture. Following the steps below, this is what happens:

    Initial State: Both switches (A & B) are down and the light is off.
    Step 1. Flip switch A up -> Light turns on. (A up; B down)
    Step 2. Flip switch B up -> Light stays on. (A up; B up)
    Step 3. Flip switch B down -> Light stays on. (A up; B down)
    Step 4. Flip switch B up -> Light stays on. (A up; B up)
    Step 5. Flip switch A down -> Light stays on. (A down; B up)
    Step 6. Flip switch B down -> Light turns off. (A down; B down)

    I don't have a diagram of the lighting, and also there is another switch in both of the switches receptacles.
    So, its A & 1 next to each other and B & 2 next to each other.
    - A & B control inside entry light
    - 1 controls outside lights
    - 2 controls living room wall light.

    Does this sound like it could be a common problem or what can I do, or my friend to narrow down the possible errors?

    Let me know if you need any more info.


    Thanks.

  2. #2

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    You have a three-way miswired. Here's how to correct the problem:

    1. Shut off the power and remove the wires from the switches. There will be three wires to each (not counting the ground if there is one.)

    2. Turn the power back on, and one of the 6 wires will be hot. Mark that wire as 'common.' Turn the power back off.

    3. Hook the 'common' wire to the common terminal of the switch. The terminal will either be marked 'common' or be a different color than the other two.

    4. Hook the other two wires to the other two terminals. It doesn't matter which goes where.

    5. Turn the power back on, and go the the other 3 wires. One will be hot. Move the switch at the other location, and another wire will be hot. Mark the wire that was never hot as 'common'.

    6. Turn the power back off, and hook 3 wires to the second switch the same as steps 3 & 4.

    7. Reinstall the switches into the boxes, put the covers back on, and restore the power. If you did it right, it will work right.
    Just my 2 worth.

  3. #3
    DIY Senior Member BrianJohn's Avatar
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    480 EXCELLENT EXPLANATION....And your friend the electrician, DO NOT LET HIM DO ANY WORK FOR YOU

  4. #4

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    I know it's a 50/50 chance, but I'll put my money on the problem being in Switch A.
    Just my 2 worth.

  5. #5
    DIY Member gfe76's Avatar
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    ok, good explanation, but what about this: just moved into house where hall light has 3 different wall switches. switch A is at bottom of stairs, switch B is at top of stairs, switch C is at one end of hall and switch D (yes 4 switches) is at other end of hall. these switches have to be in just the right position of A and C to control the light...what is going on here? how do I trouble shoot this setup? thanks

    I also have similar problem as initial poster with downstairs hall light switches (only 2) which I will trouble shoot as previously described.

  6. #6
    DIY Member gfe76's Avatar
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    I said 3 switches, but as described, there are 4.

  7. #7
    Plumber jimbo's Avatar
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    Quote Originally Posted by gfe76 View Post
    hall light has 3 different wall switches. switch A is at bottom of stairs, switch B is at top of stairs, switch C is at one end of hall and switch D (yes 4 switches) .

    Same idea. First, in your case, it is a combination of 3 way switches ( at the ends) and 4 way switches ( the 2 in the middle ). Either someone replaced a switch with the wrong type, or they mixed up the travelers and the hots. Here is a diagram which may be helpful:
    http://www.wfu.edu/~matthews/misc/sw...Animation.html

  8. #8
    Moderator & Master Plumber hj's Avatar
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    Default switches

    The testing sequence should be, (starting with the light off), and properly wired switches.
    1. Flip switch A, the light comes on.
    2. Flip switch B, the light goes off.
    3. Flip switch A, the light comes on.
    4. Flip switch B, the light goes off.

    There should be no position where flipping switch B does not turn the light off if it is on. In an improperly wired sequence, B will turn it off, but A will not turn it back on. Your sequence of operation implies something more drastic than just a wrong wiring setup.

  9. #9
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Sparky, that was great; sure beats trial-and-error.

    It's easy enough to draw a diagram that will cause the switches to behave as described, but I'm betting on Switch B being wrong. It's conceivable that at some time in the past the original 3-way Switch B crapped out, and they replaced it with an SPST switch, connecting one traveler and the common to one switch terminal, and the other traveler to the remaining terminal. That would result in the situation described.

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