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Thread: Two lights on Two 3 way Switches...Only one comes on?

  1. #1

    Default Two lights on Two 3 way Switches...Only one comes on?

    K here is my deal....

    I ran 12/2 from my panel to a 3 way switch....then 12/3 to a ceiling light and then to another ceiling light then to a wall mounted 3 way switch....(hallway if you were curious).....

    When I throw the switches...one light comes on...the second comes on for a brief second and then goes out (florescent lights).......

    Red Wire..runs the entire distance from Switch to Switch.
    Ground Does the Same...
    The White Neutral is what the Lights are wired into both one after the other in sync and only with the 12/3 wire...neutral.

    I realize that there are several ways to wire a 3 - Way switch configuation like this but I'm not sure if this problem is my wiring or just a bad flourcent light unit?

    Anyone ever wired a Switch - Light - Light - Switch in this way with only 12/3 wire?

    Thanks.....Jeff

  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by IPictureU View Post
    I'm not sure if this problem is my wiring or just a bad flourcent light unit?
    Well it sure ain't the light.

    Quote Originally Posted by IPictureU View Post
    Anyone ever wired a Switch - Light - Light - Switch in this way with only 12/3 wire?

    Thanks.....Jeff
    No cause it just won't work wired like that.

  3. #3
    Electrician Chris75's Avatar
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    Should have ran a 4 conductor between the two lights...

    Next time, draw it on paper first...

  4. #4

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    I was afraid of that......yep I should have checked with the experts first....Darn it....

    ~ Jeff

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    In the Trades Bob NH's Avatar
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    The best way to fix it is to connect one light in the normal way. Then run 12/2 from that light to the second one.

    Using that approach you can put as many lights as you want on a pair of 3-way switches.

  6. #6

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    Run a 12-2wG from one light to the next light. The second light has no neutral. Do NOT try to use the bare ground as a conductor!!

  7. #7
    Moderator & Master Plumber hj's Avatar
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    Default lights

    A 3 way switch has 3 terminals but your wiring could only connect to 2 of them. It appears that the lights are wired in series using the neutral wire, although even that does not seem logical, but is what your description implies. A wiring diagram might eliminate the discrepencies. Your wiring sounds like one I came across years ago with a DIY'er. He wired the circuit for multiple 3 way switches. When I told him he needed 4 way switches for the extra ones but that he only had the three wires that a 3 way switch uses. When I told he he needed a fourth wire for the 4-way, he asked if he could use the bare ground wire for the fourth one.

  8. #8
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by ked View Post
    The second light has no neutral.
    Huh? .

  9. #9
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Mikey View Post
    Quote Originally Posted by ked View Post
    Run a 12-2wG from one light to the next light. The second light has no neutral. Do NOT try to use the bare ground as a conductor!!
    Huh?.
    I didn't know that any 120 volt circuit had a neutral either!

  10. #10
    In the Trades Bob NH's Avatar
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    Quote Originally Posted by hj View Post
    A 3 way switch has 3 terminals but your wiring could only connect to 2 of them. It appears that the lights are wired in series using the neutral wire, although even that does not seem logical, but is what your description implies. A wiring diagram might eliminate the discrepencies. Your wiring sounds like one I came across years ago with a DIY'er. He wired the circuit for multiple 3 way switches. When I told him he needed 4 way switches for the extra ones but that he only had the three wires that a 3 way switch uses. When I told he he needed a fourth wire for the 4-way, he asked if he could use the bare ground wire for the fourth one.
    Using a 4-way switch to allow more than 2 switches in a 3 way/4 way circuit doesn't require any more conductors. You can put as many switches as you want in the circuit using 3 conductors (not including the ground) to turn on the first controlled light that can be within the switch circuit or connected at either end. Then you run a 2-wire + ground from that controlled light to all other lights using branches and runs in the most convenient routing.

    The idea is to lay out the circuit to operate one light. Get that one working and go from there to all of the others.

  11. #11
    Electrician Chris75's Avatar
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    Quote Originally Posted by jwelectric View Post
    I didn't know that any 120 volt circuit had a neutral either!
    Way over some peoples heads....

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by Chris75 View Post
    Way over some peoples heads....
    Well, they are ceiling lights...

  13. #13
    Moderator & Master Plumber hj's Avatar
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    Default 4 way switch

    His switch was off line, rather than inline between the two three ways, so he had to have 2 traveler wires to the switch and 2 back to the second switch. He only used a 14/3 wg because that is what a three way switch would require. And I know how a 4 way switch fits into the circuit, which is why I could advise him as to his problem.

  14. #14

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    The following diagram shows what is going on with the switches with two 3-way switches.

    http://www.selfhelpandmore.com/switchoutlet/3way/

    It is possible you wired the two lights in "series" rather than in "parallel". The following page has diagrams of batteries connected in series vs parallel so you can get the idea. Imagine the batteries as being light bulbs...
    http://www.freesunpower.com/battery_diagrams.php

    The light fixtures should be connected in parallel.

  15. #15

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    Here is a diagram showing two 3 way switches and 2 light fixtures (with light fixtures connected in "parallel" as they should be)...

    http://www.handymanwire.com/articles/3wayb.jpg

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