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Power at light but not working

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  • 18-08-2017 10:56pm
    #1
    galteeboy
    Registered Users Posts: 58 ✭✭


    Have a light that has stopped working. When I check the incoming cables I have 240volts when switch is turned on but once I connect the cables to anything the power goes, any explanation for this.


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    #2
    aido79
    Registered Users Posts: 5,374 ✭✭✭aido79


    galteeboy wrote: »
    Have a light that has stopped working. When I check the incoming cables I have 240volts when switch is turned on but once I connect the cables to anything the power goes, any explanation for this.

    What type of light fitting is it? What do you mean by "the power goes"? Do you mean it trips the breaker?


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    #3
    TheChizler
    Registered Users Posts: 9,455 ✭✭✭TheChizler


    At what points are you measuring the voltage? What are you connecting as a load?


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    #4
    galteeboy
    Registered Users Posts: 58 ✭✭galteeboy


    aido79 wrote: »
    What type of light fitting is it? What do you mean by "the power goes"? Do you mean it trips the breaker?
    It's a fancy enough fitting but the light isn't the problem as I tried a regular pendant also. When the incoming cables are not connected to anything I am getting 240 between live and a neutral and live and earth when the switch is on and 50 volts when switch is off but when I connect the cables to the light or even just put them in connectors I am getting 0 volts.


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    #5
    aido79
    Registered Users Posts: 5,374 ✭✭✭aido79


    galteeboy wrote: »
    It's a fancy enough fitting but the light isn't the problem as I tried a regular pendant also. When the incoming cables are not connected to anything I am getting 240 between live and a neutral and live and earth when the switch is on and 50 volts when switch is off but when I connect the cables to the light or even just put them in connectors I am getting 0 volts.

    I think it's time to call an electrician. I highly doubt the problem is the light fitting. It may be a fault somewhere else in the circuit. There may be a problem with the switch if you are still getting voltage with the switch off. It's very strange that the voltage drops to zero when you put it in connectors.


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    #6
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    aido79 wrote: »
    . There may be a problem with the switch if you are still getting voltage with the switch off. It's very strange that the voltage drops to zero when you put it in connectors.

    Might be a few volts present if it was 2 way switching, which also disappears when a load is connected.

    Clearer info needed from op. Is there anything between live and earth when the lamp is connected? If that is still 240v then the neutral probably has an open or bad connection. Most of the supply voltage might then appear in a digital meter but disappear when a load is connected.

    A very bad connection on the live could also cause it, and would show the same voltage live to earth as live to N with load connected if that was the problem.


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    #7
    aido79
    Registered Users Posts: 5,374 ✭✭✭aido79


    Bruthal wrote: »
    Might be a few volts present if it was 2 way switching, which also disappears when a load is connected.

    Clearer info needed from op. Is there anything between live and earth when the lamp is connected? If that is still 240v then the neutral probably has an open or bad connection. Most of the supply voltage might then appear in a digital meter but disappear when a load is connected.

    A very bad connection on the live could also cause it, and would show the same voltage live to earth as live to N with load connected if that was the problem.

    50 volts is more than a few volts. I agree though that more info is needed. It's a difficult one to diagnose with the information provided.


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    #8
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    aido79 wrote: »
    50 volts is more than a few volts. I agree though that more info is needed. It's a difficult one to diagnose with the information provided.

    Its all relative really. For a digital meter to read 50v from the load point of a 230v circuit, there has to be an extremely high impedance in the circuit, near 5 times that of the meter seeing 50v (Usually capacitive coupling/open circuit). For example, 2 way landing light switched off in my house read about 30v at pendant when i tested a few years ago with a digital meter, and almost nothing with an analogue one. Which is correct?
    Both are correct

    It read zero with the bulb in, for what should be obvious reasons.


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    #9
    galteeboy
    Registered Users Posts: 58 ✭✭galteeboy


    Sorry for the delay getting back. It's a light that is switched 3 ways. No there is no voltage between anything when lamp is connected. Even when I touch the bare cables of the lamp off the incoming cables it don't work even though there is 240 at the incoming cables before anything is connected.


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    #10
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Check connections at the switches as well, and that the switches are each switching cleanly with no sign of sticking etc.


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