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  1. #1
    Join Date
    Mar 2014
    Posts
    5

    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
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    738

    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
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,841

    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
    Join Date
    Mar 2014
    Posts
    5

    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
    Join Date
    Mar 2014
    Posts
    5

    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
    Join Date
    Mar 2014
    Posts
    5

    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.

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