power at light fitting but no light

[johnhewitson]

hi all, a light in my friends house has stopped working about the time a different light switch was changed. took the bulb out and there is power at the fitting, its a two way switch and they are both working as power goes off when switches are off. tried different bulbs and none working.
the switch that has been changed runs another light upstairs which still works fine. can it be anything else where the problem is???
any help welcome.
thanks.

 

[PrenticeBoyofDerry]

Two/Three questions
1 & 2) How are you proving there is power at this fitting and what voltage value are you getting?
3) Did you rewiring the switch as it was originally, note that not all two way switches are the same with regards to terminal positions?

 

[johnhewitson]

thanks for reply. used electricians screwdriver on pins inside light fitting, goes on and off with switches. pretty sure other switch was wired up the same. all other lights working fine though. the switch that was changed is a room away from the none working light so would it be direct to that one? it doesnt trip the power anytime.

 

[flameport]

Neutral disconnected

 

[johnhewitson]

Surely if any wires were not connected or connected wrongly it would trip elec? How can there be power in light fitting but no bulb works?

 

[JohnW2]

How can there be power in light fitting but no bulb works?

The bulb will only light if current flows through it (from live wire to neutral wire). You have demonstrated that electricity is probably getting to the fitting through the live wire. However, if, as flameport suggested, the other wire (neutral) is not connected properly (at the light fitting or elsewhere) there will be nowhere for the current to flow to, hence the bulb won't light.

Kind Regards, John

 

[ban-all-sheds]

used electricians screwdriver on pins inside light fitting

Which just proves how useless they are.

Surely if any wires were not connected or connected wrongly it would trip elec?

How could a wire not connected cause a protective device to operate?

How can there be power in light fitting but no bulb works?

http://www.google.co.uk/search?q=electrical+circuits+101

 

[PrenticeBoyofDerry]

thanks for reply. used electricians screwdriver on pins inside light fitting, goes on and off with switches. pretty sure other switch was wired up the same. all other lights working fine though. the switch that was changed is a room away from the none working light so would it be direct to that one? it doesnt trip the power anytime.

Neon test screwdrivers that is your first problem, no good as an accurate or safe means of testing. Either bin it or use it only as screwdriver.
To test for voltage you require a two pole/probe detector that will measure the value of volts being measured, between two reference points, these generally being L-E, L-N and N-E. That should give you information you require regarding voltage issues, a test screwdriver cannot perform these functions.

If a conductor is not connected or loose, it will not operate a safety device, and if in your case it is a neutral or switch line, it will not operate the light neither.
The safety device will only operate if the circuit is overloaded or shorted, not if a conductor is in free air.
Even though this is a simple and basic tasks, you or your friend (whoever is the responsible party?), do require some basic but suitable test equipment, which a test screwdriver is not.

 

[Taylortwocities]

hi all, a light in my friends house has stopped working about the time a different light switch was changed.

That's your hint as to where the problem may be.
It is a MASSIVE clue if a circuit has been working for 20 years and then stops at about the same time a switch has been changed.

 

[johnhewitson]

Thanks for all the help guys. I'll have another look today. I guess this is why people who don't know what their doing mess around with electricity. Cheers.

 

[PrenticeBoyofDerry]

Thanks for all the help guys. I'll have another look today. I guess this is why people who don't know what their doing mess around with electricity. Cheers.

And test with a two pole detector, not dodgy neon screwdriver!

 

[JohnW2]

Neon test screwdrivers that is your first problem, no good as an accurate or safe means of testing. Either bin it or use it only as screwdriver. To test for voltage you require a two pole/probe detector that will measure the value of volts being measured, between two reference points ...

Whilst I'm sure that we would all agree with that as generalisation, in this case I think that the neon screwdriver has served a useful purpose - since the neon goes on and off in response to operation of the switch, it shows without almost any doubt that L voltage is getting to the fitting (albeit it could be through a high impedance connection) - which I presume is why flameport concluded that there was probably a 'disconnected neutral'.

Confirming that would, of course, theoretically be easy with a 2-pole tester, since it would show ~230V L-E, but little or no voltage L-N, at the fitting. However, even then one could get misled if one used a high-impedance 2-pole tester (which most of them are), since it might show a fairly normal L-N voltage even if there were a very poor connection in the neutral. ... one has to remember that (high impedance) 2-pole testers are not necessarily a panacea.

Kind Regards, John

 

[johnhewitson]

hi all, i've checked all connections which were all secure. tried putting another switch onto the one that was changed earlier (which was suspected to be the problem) but still the same. havent tried a 2 pole tester on it. could there be anything else? there has been carpet fitters in the house. could a nail through a cable cause this problem?
is it just time to call in someone who knows what their doing?
cheers.

 

[deadshort]

Hi, it's very possible that the carpet fitting activity may have caused an already loose connection in a join box to become disconnected. if the carpet was fitted above the room that the light is in.


Regards,

DS

 

[Ne11yboy]

Same problem here but lights on a dimmer switch

power to light pendant reads as per 230 and tiny 0.3

wonder if my issue is a broken cable inside the flex