Disappearing voltage

[richy3333]

THOUGHT YOU'D USED YOUR LAST GASP....... A BIT LIKE THE LABOUR PARTY. :devil2:

Sorry who? Didn't they turn the lights out as they left the room

 

[Marvo]

The waveform that a dimmer supplies can give false readings with voltage and current testing because it's a chopped waveform sometimes with higher frequency than normal electrical supply. As mentioned remove the dimmer and test the circuit with a normal switch. Once you're sure it's fault-free then reconnect the dimmer.

 

[amckay]

Has he been playing diy with any of the other fittings on that circuit and there's a loose N somewhere?

 

[shanky887614]

I only tested between line and earth

should have checked between L-N you could have a broken N at the light

What are you testing the voltages with? please say it is a two probe voltage tester or a multimeter.

a lot of multimeters are affected by ghost voltages, analogue multimeters are not usually affected as much as they put a lot more load on it when they test V.

i would have thought a drummold test lamp would be the easiest to see if it is ghost voltage (no light then its a ghost voltage)

you can get an adapter to put in you mm which will put a load across your test leads

en-us.fluke.com/products/all-accessories/fluke-sv225.html#features

basically the above is useful if you dont have an analogue multimeter

 

[HappyHippyDad]

240V which is there with no load, but disappears when load is connected is better known as a ghost voltage.
Why on earth did you think that replacing the light fitting would fix a problem with the switched live not becoming live?
For a ghost voltage to appear on the switched live then it is most likely that this is no longer connected to where it should be. I'd go with a wire broken off at one of the switches or a faulty dimmer.

Do you really think this would be ghost voltage in this instance? I dont understand how the 'amount' of ghost voltage is determined, but is 240V rather a large figure?
When I did my little, very unscientific experiment with 30m's of 1mm 3 core I got a maximum of 91V, I doubt the OP has 30m's going between the switch and the light. http://www.electriciansforums.co.uk...-odd-request-regarding-phantom-voltage-2.html

 

[davesparks]

I've only ever seen or been told of it mimicking the actual mains voltage.
I've only seen a measured value myself a few times, the above symptoms are typical for what I've been told in the past when I've arrived to find such a fault.
Normally I use my AVI and only get one little red LED when there's a ghost voltage present so rarely put a value to it