Discuss Problem wiring light switch any guidance welcome in the Electrical Forum area at ElectriciansForums.net

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wobblymike

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I have a dimmer switch in my lounge feeding 2 wall lights, they were installed before I moved here. The other day the switch failed so I bought a new one and went to fit it when I removed the old switch I discovered three 3 core cables in the switch box I; l will call them Cables 1,2 and 3. Cable 1 red wire is a permanent live feed which connects to one side of the switch, its earth wire connects to the earth tag on the switch its neutral wire was lying loose. When I measure the voltage on cable 1 - it measures 230v between live and earth, 0 between live and neutral and 0 between nuetral and earth. Cable 2 is connected to the wall lights, its live feed was connected to the other side of the switch its earth wire was lying loose its neutral wire was connected via choc block to the neutral wire of cable 3. Cable 3 live and earth are lying loose. I discovered that Cable 3 goes to a 3 pin mains socket about 2 feet away from the switch and that within the socket its neutral cable is connected to the neutral pin on the socket. WOW

By disconnecting everything I consider it ought to work as follows:
cable 1 live connects to one side of switch - cable 2 live to other side of switch - cable 2 neutral then needs to connect to cable 1 neutral. However when this is done it doesn't work and when I measure between live and neutral it reads nothing regardless of whether switch is closed or open. I conclude that neutral line on cable 1 is broken somewhere and someone has run a cable to adjacent socket connected up the neutral and then connected cable 2 neutral to it.

Grateful for any opinion on my conclusions
mike
 
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Guest123

  • Thread Starter Thread Starter
  • #2
Hey Mike.

Sound like you've had a right bodger in there.

First of all you shouldn't really be re-connecting that switch with the neutral being "spurred" off of a socket circuit,. it's down right dangerous.

Ideally you should be running a new feed to that switch off of your lighting cicuit.

Cable 1 appears to have been the original feed to your switch so I would suggest trying to find out where this is terminated - check other switches or light fittings in close proximity to the switch.

Are you a sparky Mike????

If not it sounds like a problem a sparky should be checking out for you as it will need to be checked by proper testing to make sure it is safe i.e IR, Zs, RCD test (if there is one)

Cheers.
 
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wobblymike

  • Thread Starter Thread Starter
  • #3
Lenny

Thanks for the response - I'm not a sparky but I am an electronics engineer so a kindred spirit I guess and I have done a fair bit of domestic electrics.

When I have had the switch out and all the wires disconnected and lying loose all the other lights in the house work ok. The cable is a 3 core 1.3mm cable red, black amd green and yellow I am surmising that it was the same cable that fed the ceiling lights before they were removed - I have checked the light switches in the vicinity - no such cable. My conclusion is that the cable must be connected to the live feed up in the ceiling where the previous lights were and that the neutral has been overlooked or come loose. What do you think?
 
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Guest123

  • Thread Starter Thread Starter
  • #4
Hey Mike.

Sounds like the Cable "feed" is either terminated at or above one of your other light fittings or in a joint box which in itself is a bit naughty as screw terminal joint boxes are supposed to be accessible for inspection.

It really needs repairing properly i.e neutral from lighting circuit not socket crcuit and testing to make sure it's safe to use.

Whilst replacing a broken light switch is not notifiable under part P of the building regulations I'm afraid the installation of new wiring is.

Also I would advise perhaps having a periodic inspection by an electrician to find out if there any other problems with the installation in your home as it sounds like the previous owner was a right dodgy DIY'er

Cheers.

Ben.
 
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johnnyb

  • Thread Starter Thread Starter
  • #5
Get someone to check the rest of the house matey, as you have found that mess now, sods law says that theres other things wrong as well.
 

Had8Lives

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Arms
While I agree it's worth getting the wiring checked, a possible solution to the problem using the existing wiring would be to install a fused connection unit next to the socket with a 3 or 5 amp fuse in it (depending on what wattage your wall lights are)and use Cable 3 to supply your live feed to the switch your earth and your neutral. Then if the feed to cable 1 cannot be found, put the live and neutral coloured wires in separate connector blocks and tape them up.
 
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