Troubleshooting two 3-way switch setups

Discussion in 'Electrical Forum discussion & Blog' started by Thatguy, May 7, 2009.

  1. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    This assumes two travelers between the switches.

    Assign each switch a number.
    With switch #1 & switch #2 down, light is on or off?
    With #1 up & #2 down, light is on or off?
    With #1 down and #2 up, light is on or off?
    With #1 & #2 up, light is on or off?

    In principle, with the answers filled in, the problem(s) can be pinpointed.

    Test cases welcome. . .
  2. sakkyoku

    sakkyoku New Member

    Messages:
    2
    off
    off
    on
    off
    Looks like I'm the first test case. How do I fix it?
    Thank you in advance.
    Last edited: May 21, 2009
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
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    Location:
    Cave Creek, Arizona
    switch

    It appears that one of the travelers is connected to the common on one of the switches, therefore there is only one configuration where both are "on" to let the lamp operate.
  4. Thatguy

    Thatguy Homeowner

    Messages:
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    Location:
    MD
    Sw#1 is working like an on/off switch when #2 is up. When sw 2 is down there is no continuity.
    Either a traveler is not connected or it's like HJ said.

    Set both switches down so the controlled lamp is off.
    Assuming two travelers, like in most of the diagrams in this link
    http://en.wikipedia.org/wiki/Switch
    if you run a wire from the common of one switch through a 100w incand. bulb to the common of the other, the test light and the controlled (incand.) light should go on, equally faintly if they are both the same wattage. You can then safely put a piece of wire in place of the test bulb and you should get full brightness on the controlled light.
    If not, the wires feeding the common switch terminals are incorrect.

    You'll need an extension cord and clip leads.

    Never and I mean Never try anything that comes close to this. This is very dangerous and should never be attempted

    Thatguy this will be deleted should you ever post anything like this again. If you disagree PM me and we will discuss the safety issues involved.
    Last edited by a moderator: Aug 25, 2011
  5. sakkyoku

    sakkyoku New Member

    Messages:
    2
    thanks

    I had switched a traveler and the common on both switches.
  6. golong27

    golong27 New Member

    Messages:
    1
    next case...

    off
    off
    off
    on

    I'm replacing the old dirty switches with new white ones and have two different 3-ways with the same behavior.

    switch #1 is the end of the circuit and #2 is in the middle.

    thanks in advance.
  7. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    Check the switches using an ohmmeter as to operation and terminal labelling.

    Check that the common switch terminals go to the right wires and not one of the travelers.

    There is a slight chance that hooking up the switches incorrectly will damage a good switch so I'd run the light bulb test, but it is a bit inconvenient.

    NEVER use a light bulb tester for checking voltages
    Last edited by a moderator: Aug 23, 2011
  8. Donwe

    Donwe New Member

    Messages:
    5
    Location:
    Bend, Oregon
    Ok, here's mine.

    off
    on
    off
    off

    Thank you for your time.
  9. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
    MD
    Assuming you have wired the switch common terminals [different color than the other two] and traveler terminals [same color] correctly, one of your travelers is open or one switch is internally defective in that there is no continuity between the common terminal and the traveler terminal when the switch is thrown to that position.
    It's an SPDT switch.
    http://upload.wikimedia.org/wikipedia/commons/thumb/b/b6/SPDT-Switch.svg/325px-SPDT-Switch.svg.png
    Last edited: Nov 5, 2009
  10. Donwe

    Donwe New Member

    Messages:
    5
    Location:
    Bend, Oregon
    Thank you that was very helpful.
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
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    wires

    We do not know what the wire colors are in your circuits, but the hot and "hot" to the light go on the bright brass terminals. The travelers, which might both be the same color, but should be the only two left when the proper wires are on the common, attach to the two dark colored terminals. They can be connected to either one.
  12. Thatguy

    Thatguy Homeowner

    Messages:
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    Location:
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    The travelers may have phantom voltages on them, so use a 120v incandescent bulb to check for voltages. Most testers will respond to phantom voltages.

    NEVER use a light bulb tester for checking voltages
    Last edited by a moderator: Aug 23, 2011
  13. Jim Port

    Jim Port Electrical Contractor

    Messages:
    156
    Location:
    Maryland
    Normally the traveller screws are brass colored. The common is typically the dark colored screw.
  14. Donwe

    Donwe New Member

    Messages:
    5
    Location:
    Bend, Oregon
    OK, so it was a bad switch, thank you again:)

    Here's a better one, I have three switches controlling an overhead kitchen light, switch one is a three way and is where the circuit starts and I have confirmed the hot leg is connected to the common post, switch two is a four way, and switch three is a three way. the problem is switches one and two will only control the light if switch three is on, any ideas?
  15. Thatguy

    Thatguy Homeowner

    Messages:
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    Location:
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    Post what you believe to be the schematic.
  16. Donwe

    Donwe New Member

    Messages:
    5
    Location:
    Bend, Oregon
    --- s === s === s --- o
  17. Thatguy

    Thatguy Homeowner

    Messages:
    1,459
    Location:
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    Your schematic leaves something to be desired, but I think a traveler for sw 3 is missing
    or the 4-way is wired incorrectly or is bad.

    BTW, 'on' is not defined for 3-ways and 4-ways; that's why they are not labelled like other switches.
  18. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,811
    Location:
    Cave Creek, Arizona
    wires

    All it takes is for the common and a traveler to be interchanged and the circuitry will not operate properly. Mixing "line 1/A and 2/B" on the four way can also cause weird operation.
  19. Donwe

    Donwe New Member

    Messages:
    5
    Location:
    Bend, Oregon
    Thats what it was, once I isolated the traveler pairs and re-connected everything works just fine, Thank you!
  20. alth

    alth New Member

    Messages:
    4
    Location:
    Canada
    Trouble with 3way Switch!

    Hi there hope you can help:

    Will a 3 way switch with the following configuration work for my stairs to basement, and if it will how can I fix it:

    Live Feed
    l
    l
    Switch #1 ---- Switch #2------ Light # 2
    l
    l
    l
    Light #1

    When Switch #1 is on and Switch #2 is off Light #1 works but Light #2 does not

    When Switch #1 is on and Switch #2 is switched Light #1 turns off and Light #2 turns on

    When Switch #1 is off and Switch #2 is switched nothing happens

    Thanks for the help!
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