Help With Basic Light Wiring

Barns · Jan 4, 2017

An old small tubular striplight in a desk/cubby hole in my aged parents' house has gone and it seemed silly to call out an electrician for one small light so I said I would help.

Obviously, I thought it was just the bulb but tried the bulb from the bedroom next door, which has exactly the same light fitting in exactly the same desk/cubby hole arangement. The bulb worked fine in that room when I tested it but didn't work in the first room. Funnily enough, when I put it back in the second room and tested it again that light didn't work either so now both lights are not working.

I also tried brand new bulbs in both lights but no dice.

As a result, I thought that a wire must have come loose on the first light and it led on to the next one so both had stopped working.

So, I unscrewed the first light fitting from the wall and could see that the two earth wires (green and yellow) were twisted together as expected but hanging loose and one of the three terminals in the light fitting had no wires going to it so, presumably, they should be reattached to that terminal. The rest seems right with the two red wires connected together and to nothing else and the two black wires going into seperate terminals in the light fitting. (see pic)

However, I tried, very carefully obviously, touching them on to the third terminal twice, with cord switch pulled inbetween to make sure it was on, but still no luck.

I know the basics of electrics and have done a few DIY projects before, but am certainly not an expert so thought I'd ask for some advice.

Am I correct in thinking the green and yellow wires should be twisted together and attached to the third terminal?

Should the light not work anyway even without the earth wires attached? If so, am I right in thinking that that suggests a problem somewhere else in the house wiring?

Here's the pic:

[ElectriciansForums.net] Help With Basic Light Wiring

Thanks in advance for any help.

View attachment 35107

Andy78 · Jan 4, 2017

With respect, I think you should call an electrician who possesses the correct knowledge and equipment to sort this for you.

David Prosser · Jan 4, 2017

That looks a bit bodged, get an electrician in or are you still in Loas ?

westward10 · Jan 4, 2017

Your latter assumptions are probably correct. The two blacks and reds are probably connected correctly to switch it. But as the previous posts say get an electrician in to rectify/replace the fittings.

Barns · Jan 4, 2017

DAvid Prosser said:
That looks a bit bodged, get an electrician in or are you still in Loas ?

lol, I've finally managed to escape from Laos and have been back in the UK for a few weeks now.

I don't think it's bodged as such, although you would obviosuly know far better than me. It was just done 40+ years ago so, presumably, standards have improved since then.

If you both think it's just better to get an electrician in then that's what I'll do. These sort of projects were quite fun back in rural Laos when even I was better than the local electrician, but so many other things to do back here in the UK I'll just get a sparky in.

Thanks all.

Hellmooth · Jan 4, 2017

More than likely the light fittings are at fault, but with the lack of knowledge you would be best getting a spark in!

Taylortwocities · Jan 4, 2017

Its not clear what sort of light fitting you have there, but some of the tube light fittings (that are designed for bathrooms) will not work until the cover is replaced to cover the lamp itself. It's a safety feature to stop people putting their fingers on the live ends of the lamp.

And as an aside

Barns said:
presumably, standards have improved since then.

Regretably, not at all

Barns · Jan 5, 2017

Taylortwocities said:
Its not clear what sort of light fitting you have there, but some of the tube light fittings (that are designed for bathrooms) will not work until the cover is replaced to cover the lamp itself. It's a safety feature to stop people putting their fingers on the live ends of the lamp.

And as an aside

Regretably, not at all

You're a star mate. That's exactly what it was!

My electrics were correct, I just didn't know about the switch which breaks the circuit unless the cover is on and I was testing without the cover on. So, the whole problem was just a simple blown bulb in the first place... Doh!

Just shows how useful forums such as this can be!

Thanks all of you for your time and advice. Both lights working fine.

However....just to test, I didn't reattach the two earth wires to the third terminal, but did make sure they were well clear of the blacks and reds.

Now, and correct me if I'm wrong, an earth wire for a light fitting is to avoid any metal bits going live, yes? This entire unit is plastic and the wires are impossible to touch without removing the cover and bulb and then unscrewing the entire unit from the wall. (see pic)

Now, obviously, best practice would say to switch off all the lighting circuits in the house at the circuit board and reattach the earth terminals, but is it really that important?

I probably will do it next time my folks are out of the house and I can switch all the lights off without confusing them anyway, but just out of electrical curiosity, does it matter? And, if so, why?

View attachment 35113

westward10 · Jan 5, 2017

It isn't clear from the picture but the terminal appears to have an "E" next to it which should be earth. The fitting may or may not need an earth, there could be some internal parts which require an earth so yes connect the cpcs to the terminal. PLEASE ISOLATE FIRST FOR SAFETY. Glad the problem is resolved.