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  1. #1
    Join Date
    Dec 2008
    Posts
    18

    Default Ceiling Electrical box problem

    Hi,

    I found a problem while trying to replace a ceiling light fixture, but I'm not sure how to fix it. The old fixture worked, but when I put the new fixture on it wouldn't work. If I put a voltage detector on the hot wire, sometimes it confirms the wire is live but sometimes it doesn't (50/50 at best). If I touch the voltage detector to the electrical box, about 75% of the time it shows as live, but every now and then it doesn't detect a live circuit.

    Any ideas as to what exactly is wrong? The wiring is probably 30+ years old and is in a vaulted ceiling, so I don't have attic access to the wiring. And I don't want to install the new light fixture on a line that isn't consistently showing a live circuit.

    Thanks for any help you can offer!!

    Dave

  2. #2
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,436

    Default Re: Ceiling Electrical box problem

    If the old fixture was working fine, that means the wires are OK.

    And if your new fixture doesn't work fine on the same wires, then there's something wrong with the installation.

    Make sure you identify each wire and connect them properly. At the same time, take a look at your breaker, make sure it's functioning properly as well. One more thing: if you have a switch, check it too.

  3. #3
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    644

    Default Re: Ceiling Electrical box problem

    The detector you're using will only work if you're standing on a surface that has some leakage to ground from you're hand.

    If the box isn't grounded and you don't have a ground wire in the feed cable and you're on an insulated ladder (like you should be)it may not work. It's just one of many tools.

    In you're case you could run a wire from a cold water pipe or ground rod and measure to each of the conductors in the box. The one that reads 0 volts is the grounded conductor and you should put a piece of white tape on it.

    The conductor that measures 120 volts to the temporary wire (ground rod) is the hot and you should place a black tape on it.

    By the way, some fluorescent lights won't work if the metal enclosure isn't grounded.

    Good Luck from Columbiana, Alabama
    Maurice Turgeon, [URL="http://thesemiretiredelectrician.com"]

  4. #4
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,621

    Default Re: Ceiling Electrical box problem

    Non contact testers are terribly unreliable. You can touch it on your arm and you will read voltage. Do not rely on such devices.

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

  5. #5
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Ceiling Electrical box problem

    Quote Originally Posted by Dmurr33 View Post
    Hi,

    I found a problem while trying to replace a ceiling light fixture, but I'm not sure how to fix it. The old fixture worked, but when I put the new fixture on it wouldn't work. If I put a voltage detector on the hot wire, sometimes it confirms the wire is live but sometimes it doesn't (50/50 at best). If I touch the voltage detector to the electrical box, about 75% of the time it shows as live, but every now and then it doesn't detect a live circuit.

    Any ideas as to what exactly is wrong? The wiring is probably 30+ years old and is in a vaulted ceiling, so I don't have attic access to the wiring. And I don't want to install the new light fixture on a line that isn't consistently showing a live circuit.

    Thanks for any help you can offer!!

    Dave
    I would guess you have a poor neutral connection.
    "" an ounce of perception -- a pound of obscure "
    - Rush

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