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  1. #1
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    Mar 2014
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    Default Turning on light disables GFCI outlet

    I replaced a bathroom GFCI outlet that I thought was not working. The new one works fine when the bathroom light is off, but when I switch the light on, the outlet goes dead. Any suggestions for diagnosing or repairing this problem?

  2. #2
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    Columbiana, Alabama
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    Default Re: Turning on light disables GFCI outlet

    Quote Originally Posted by KenB View Post
    I replaced a bathroom GFCI outlet that I thought was not working. The new one works fine when the bathroom light is off, but when I switch the light on, the outlet goes dead. Any suggestions for diagnosing or repairing this problem?
    A GFCI protected circuit detects current flow which was leaked to ground causing a dangerous situation. It then trips the power off so fast that if a person was getting shocked and was the cause of the leakage, they would not be harmed, or may not even feel it.

    In your case the following items could be the cause of the tripping:

    1) damp wiring or light fixture
    2) a staple supporting the wire, which was overdriven
    3) a nail or screw was driven into the wire
    4) a lightning strike or surge has caused the light, switch or wire to fail
    5) if the lamp is electronic such as a CFL or LED, it may have failed
    6) a wire connector may have pinched the wiring because it was overtightened during construction, years ago.
    7) there is a short in the wiring where the white or black wires and is touching the bare wire or a metal box
    8) rodents could have chewed through the wiring

    Quick checks would be: Turn off the power and; remove the lamp, light fixture or switch. Then wiggle and re-orient the wiring. Check that no wires were pinched.

    Also, go into the attic or basement and verify that no wiring has been nibbled on or damaged.

    If you still have problems an experienced electrician, with test equipment, will be needed. Do not allow the GFCI protection to be removed, it is a valuable safety device.
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

  3. #3
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    Default Re: Turning on light disables GFCI outlet

    When you say it goes bad, do you mean it no longer supplies power but when the llight switch is off it does, or do you mean it trips when you turn on the light and then need reset.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  4. #4
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    Mar 2014
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    Default Re: Turning on light disables GFCI outlet

    Turning on the light does not trip the GFCI plug. It simply interrupts the power. When I turn the light back on, the GFCI functions again - there is a small green indicator light that comes on when the GFCI is working. Also, I have tested it by plugging in my shaver - works when the light is out, but not when the light is on. I don't have to reset the GFCI.

    There is a black and a white wire coming to the light switch (and a ground connected to the box). There is a black and a white wire connected to the GFCI plug (and ground wire connected to the box).

    I've done a good bit of my own wiring (recently wired my new garage and the inspector noted it was very good work), so I know about safety, and connecting things properly. But I need some advice about diagnosing how this particular configuration might have been incorrectly hooked up by the previous owner.

    Thanks for your help.

  5. #5
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    Mar 2014
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    Default Re: Turning on light disables GFCI outlet

    To further test, I removed the GFCI plug. When the light is switched off, the black wire at the plug has current (according to my handy-dandy tester) and the white wire at the plug has no current indicated. When the light switch is on, neither black or white wire at the plug indicates any current.

  6. #6
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    Mar 2014
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    Default Re: Turning on light disables GFCI outlet

    More investigation. I removed the light fixture. 3 sets of wire come into that box. All of the white wires are connected together. (The light has 2 bulbs with a black and white wire from each of the two sides). The black wires from the fixture are connected to one of the black wires coming into the box. The white wires from the fixture are connected to two of the black wires coming into the junction box.

    So I expect that my problem lies in this set of connections, but don't know how to figure out which wire comes from the switch, which comes from the GFCI plug, and which one (I assume) is the power source, or heads in some other direction.

  7. #7
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    Default Re: Turning on light disables GFCI outlet

    It is wired incorrectly. You will need to break all connections at the light and GFCI and shut the power off. Turn the switch on an check with a continuity checker to see which set of black white wires read 0 ohms. That is the switch loop. Turn off the switch and jumper the black an whit at the GFCI together and test for ) again . That pair is for the GFCI. The last set should be the house power. Connect the house neutral (white)to the white going to the lights and the white going to the GFCI. Mark the white on the switch loop with black marker and connect it, the black to the GFCI, and the house black together. Connect the black from the switch to the black to going to the lights.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  8. #8
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    Jan 2011
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    Columbiana, Alabama
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    Default Re: Turning on light disables GFCI outlet

    Quote Originally Posted by KenB View Post
    More investigation. I removed the light fixture. 3 sets of wire come into that box. All of the white wires are connected together. (The light has 2 bulbs with a black and white wire from each of the two sides). The black wires from the fixture are connected to one of the black wires coming into the box. The white wires from the fixture are connected to two of the black wires coming into the junction box.

    So I expect that my problem lies in this set of connections, but don't know how to figure out which wire comes from the switch, which comes from the GFCI plug, and which one (I assume) is the power source, or heads in some other direction.
    First you have to determine if power to the light is fed from the switch location in the ceiling. This will require a 120V tester. The easiest way to do this is to turn off the power and disconnect all the wires first. Then select a pair of wires, clip your tester to the black and white and turn the power back on.

    If you find a pair of wires that stay hot all the time the power is on you may assume power originates in the light fixture, and follow the instructions below.

    If power originates in the light fixture:
    Both the white wires from the lamps should be tied together and to all the other white wires in the ceiling, except the one that goes to the switch..

    Power will be sent to the switch by tying the white wire to the black wire in the fixture that is always hot. Code requires this white wire to be re-designated a "hot" by wraping a small band of black tape around it.

    All other black wires in the light should be tied together


    If power originates in the switch location:
    Both the white wires from the lamps should be tied together and to all the other white wires in the ceiling,.
    And the two black wires from the lamps should be connected together and down to the switch.

    All other black wires in the light should be tied together.
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

  9. #9
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    Mar 2014
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    Default Re: Turning on light disables GFCI outlet

    Problem resolved! Thanks for all the advice. Whoever had wired the light fixture had connected the black wire from the GFCI plug to the same bundle as the switch. I changed that one wire and everything works perfectly. A good day.

  10. #10
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    Apr 2014
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    17

    Default Re: Turning on light disables GFCI outlet

    Quote Originally Posted by KenB View Post
    Problem resolved! Thanks for all the advice. Whoever had wired the light fixture had connected the black wire from the GFCI plug to the same bundle as the switch. I changed that one wire and everything works perfectly. A good day.

    What I don't get if you simply replaced an outlet, the problem started which I would say you wired the new outlet incorrect... If the old outlet was working fine why would the light all of a sudden control the outlet?

    Either way I know how frustrating this can be.. electricity is strange in these situations. Glad you got it resolved.

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