Dodgy Lighting Cable

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21 Jan 2004
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I have 4 lights in the hallway, all controlled by the same light switch. One of the lights has never worked since I moved in.

I removed the light fitting and tested the wires with a volt meter. If the light switch is off I get approx 0 reading.

With the light switch on, if I test the live wire alone I get 22V. If I test live and earth I get 33V and if I test live and neutral I get 46V. Any ideas what this means? A loose wire somewhere?

There are a lot of 12V lights around the house and half a dozen transformers in the loft but if I test the faulty wire with the meter on DC I get 0 ready so I don't think it's connected to one of the transformers.

I've traced all the other light fittings back to a junction box in the loft but cannot find any route to the dodgy cable so I'm not able to disconnect it.
 
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If it's for halogen lighting it is modt likely AC. Read the info on the casing.
 
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Thanks for the replies. I didn't get notifications so didn't see them. Anyway, I've finally figured it out!

This is the broken cable. I didn't want to fill the hole in until I'd managed to disconnect it, as it becomes live when the landing lights are turned on.

IMG_0974.jpeg

I went into the loft again and confirmed that the 3 working lights have cables that go up the wall into the loft to a JB and then a cable down the wall to the upstairs light switch. From there a cable goes down the wall into the landing floor and then down another wall to the downstairs light switch. The broken cable does not go into the loft and when I waived a cable detector around the broken cable it showed that the cable went sideways to the left, not up to the loft.

I lifted the landing floor and there are dozens of cables there. However they were all grey except one which was white, and the broken cable is also white...

I followed that and it lead into a cupboard which I cleared out and found this poking out of the floor:

IMG_0023.JPG

It's tiny (about 2 inches in diameter) and was loose. I tested it and it becomes live when the landing lights are on but gives strange readings when live (46V instead of 230V). So I disconnected the outgoing cable and sure enough the broken cable in the wall is now dead - so I can plaster over it.

I removed that small JB completely as I don't want it poking up out of the floor like that. I traced it back to another JB in the landing floor where I could disconnect it, so there are no live ends at all now. Someone must have tried to fix it before as they'd pulled the cable up through the floor through a notch in the floorboard.

IMG_0024.JPG
 
Looking at the middle photo there is too much insulation stripped back on the blacks and reds with no sleeving over the earths. So much so that the top red entering the JB terminal looks as though it isn't actually connected properly. This may have been the origin of the first problem.
Finding something like this would make me check every other JB that I could find and, if wired in a similar fashion, to trim the cables so only the required amount of bare copper was exposed. I would also sleeve any bare earth wires I encountered. After this I would check all light switches, 13A sockets and every other outlet such as cooker, immersion etc.
 
I had an electrician round a while ago to install a new cable for the cooker. This was the comment on the certificate he left:

Untitled.png


The previous owner had a son in law who was purportedly an electrician but it's clear that all the newest changes are not of a high standard. When I had the floor up I looked at the other JBs and they look fine, totally different standard. The white cable sticks out like a sore thumb, it's much newer and not terminated properly.

The little white JB isn't something a professional would use. I looked under the floor beneath it and there's a bigger JB properly screwed to a joist. It was empty and it's clear that someone has removed the wires from it and pulled the wires up through the floor and fitted that new little JB.

When the electrician was here he did test and tidy up anything that looked dodgy but we didn't know about this bodge at the time as it's hidden away in a cupboard.
 

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