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Ceiling light not working

Discussion in 'Electronic Basics' started by johndee, Jan 10, 2007.

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  1. johndee

    johndee Guest

    This is basic, but the post is longish. I replaced the light switch in
    my house because the ceiling light would not come on. It still does not
    after switch replacement. Old switch tests as good. Using a two-wire
    device with a small lightbulb, I have tested the switch hooked up in
    off position, and the test light does not light up. On other switches
    in the house it does light up. I also tested other ceiling light
    sockets with the same device and the test light comes on. The light
    socket in question yields a no-light on the test device. My question:
    Is there a break or short in the wire from the switch to the socket, or
    is the socket bad? Related question: How do I find out where the
    possible break or short in the wire is located? Any help is
    appreciated, thank you.
  2. Rich Grise

    Rich Grise Guest

    Probe the switch box itself with your test light, from hot to neutral. If
    there is no power there, then the fault is between the box and the
    distribution panel (fusebox). If there's power to the switch, and power
    on the output side of the switch when it's "on", but still no power at
    the socket, then the fault is between the switch box and the socket. In
    that case, you'll have to open the box the socket is mounted in and check
    its connections, or go into the attic and check the wires.

    Good Luck!
  3. Sean

    Sean Guest

    Please, if you don't really know what you are doing, don't do it. Mains
    electricity is nothing to fool around with.


    If I'm reading this right, you don't have power to the switch.

    Check the connection from your fuse of circuit breaker box.

    Go to RS or Radio shack (depending on continent) and buy yourself a
    cheap multimeter. Set it to Volts and the right range, if necessary,
    and test for voltage on the wires leading to your switch.

    If there is no voltage, then the fuse is blown or the wire is
    disconnected somewhere between distribution box and switch.

    If all else fails, hire an electrician. How much is your life or your
    house worth?

    For God's sake, be careful. The worlds cemetaries have more than their
    fair share of amateur electricians.
  4. If you have not been able to nut this out without help just get a sparkie.

  5. You probably have a bad socket. Some switches only have the hot (Black)
    wire in the switch box. The neutral goes directly to the light socket.
    So a light test probe will not work across the open switch unless the
    socket is good and a bulb is in the socket to complete the path.
    Cut the wires off the light socket, strip them and turn on the switch
    and test the bare wires for voltage. You should get something if the
    wires are good. Try not to become part of the circuit.
  6. Ryan Weihl

    Ryan Weihl Guest

    sockets "wear" out, specially if you use a 100W bulb
    in a socket rated at 60W. The inner metal "spring" weakens
    with age and does not make a good contact.
    replace the socket assembly, here they cost $4.50 or so.

  7. ehsjr

    ehsjr Guest

    Nobody has mentioned this, probably because it is so
    obvious: did you replace the bulb? Depending on how
    you use the test light and how your circuit is wired,
    the test light won't light up if the bulb (or the wiring)
    is bad. Below, the hot feed goes first to the junction
    box containing the switch on 2 wires. From that junction
    box it goes to the junction box where the light is installed
    on 2 more wires, so there are 4 wires in the switch box,
    not including any ground wires.

    AC hot (black wire) --------o o------------+
    A B |
    AC neutral (white wire) ------+------+ |
    C | |
    | |

    Using a test light connected at the points I
    labeled A & B, the light will not glow if the
    bulb is bad. To say you have no power to the
    switch may be wrong - it depends on how you
    used the test light. If you have the wiring
    shown above, the test should be from A to C
    to determine whether you have power to the

    It can also be wired like this:

    AC hot (black wire)--------------+
    +-------------+ A
    +-------------+ B
    AC neutral (white wire) ---------+

    In this case, the AC feed goes directly to the junction
    box where the light is installed. The black wire feed is
    connected to a "switch loop" to go out to a different
    junction box where the switch is installed, then back
    to the light fixture junction box. Testing from A to B
    won't make the test light glow if the bulb is open.
    And, depending on the test light and the size of the
    bulb in the circuit, you may not see the test light glow
    even if the bulb is good.

    People have mentioned a bad socket - and that may very
    well be your problem. Be extra careful before messing
    with it. You have no indication to tell you when the
    power is definitely off, because the light isn't working.
    Kill the breaker for that circuit before touching the
    wiring. If you don't know which breaker it is, kill them
    all. Better to kill the breakers than yourself.

  8. johndee

    johndee Guest

    Thanks to ALL who responded. Thank you, Ed, for the diagrams. I am
    going to have an electrician look at it. I do not have the knowledge or
    equipment. All of the posts have made me more aware of just how
    dangerous this can be for one who really does not know what he is
    Again, thanks to all of you!
  9. Rich Grise

    Rich Grise Guest

    Thanks for coming back with the acknowledgement. :)

    This is a rare and valued attribute for a googlie to have. :)

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