Light permanenly ON

[Jaybee 45]

I thought I'd change a light fitting in my Mum's ( the old one belonged to Noah ).
I have done this a few times in my own house and have had no problem but this time I seem to have got the wires mixed up and the light is on permanently and wont switch off at the wall.
Some of the wires were loose in the old fitting so I didn't see where they were connected.
There are two cables coming out of the ceiling each with red,black and earth wire(just copper). I connected the two red wires together and the two black wires together and then connected them into the block attached to the new light fitting already wired (brown(red) blue(black) and green/yellow(earth).
What have I done wrong ?

 

[ban-all-sheds]

I have done this a few times in my own house and have had no problem

How come you've had no problems?

There are two cables coming out of the ceiling each with red,black and earth wire(just copper).

I would expect one to be the loop cable, and one to be the switch cable, which makes the next bit rather odd....

I connected the two red wires together and the two black wires together and then connected them into the block attached to the new light fitting already wired (brown(red) blue(black) and green/yellow(earth).

Why don't you know that some blacks at light fittings are live, not neutral?

What do you think happens when you connect live and neutral together?

As you don't mention fuses/MCBs blowing/tripping, then one of those cables can't have been a switch drop. Are you sure that there isn't a 3rd cable lurking up there?

What have I done wrong ?

Deciding it was was OK for you to fiddle with lights when you must realise that you don't know anything about how lighting circuits work?

//www.diynot.com/wiki/electrics:lighting

 

[Spark123]

Is it a dimmer switch?

 

[TicklyT]

Is it a dimmer switch?

do you mean Was it a dimmer switch?

 

[PrenticeBoyofDerry]

Two reds together
your two blacks separately connected, one to the brown flex on light, the other to the blue flex on light.
Your bare copper wire should be covered with green/yellow PVC sleeving, get some and do that, then terminate them to the earth terminals on the fitting.

 

[davelx]

Two reds together
your two blacks separately connected, one to the brown flex on light, the other to the blue flex on light.
Your bare copper wire should be covered with green/yellow PVC sleeving, get some and do that, then terminate them to the earth terminals on the fitting.

That's not likely to work. If he's described what he's done correctly, then he's connected the switch directly across L & N, so operating the switch would cause the fuse/breaker to trip. That doesn't seem to have happened, so either the switch is broken, or he's not told us everything. Hence BAS's question:

"As you don't mention fuses/MCBs blowing/tripping, then one of those cables can't have been a switch drop. Are you sure that there isn't a 3rd cable lurking up there?"

 

[1john]

is that the only light operated from that switch? or as before, is/was the light switched from a dimmer?

 

[Lectrician]

It could be one of those odd setups where one of the cables is a Live and Neutral, the cable only really being used for the neutral, the live terminated on it's own.

The other cable could be supplying the switched live from somewhere on the red, the black more than likely doing nothing, but the spark has no single core DI.

In this case, both black to the blue of the light, and one red left on it's own in a block, and the other the brown of the light. The reds could be either way around.

This would explain why no fuses blew when the switch was operated.

 

[Jaybee 45]

Thanks guys for all the replies. I think I'll get an electrician to fix it as I don't understand all the different (conflicting) views you have on the subject.
As to the slap on the wrist from ban-all-sheds, I was asking for some advice not sarcasm. I've had no problems before because I was able to see where the wires had been connected and I could replace them.
I am not one to take risks and always switch off the mains and test for any live wires.
Obviously I shouldn't meddle with things I don't understand fully, as in your field of electrics, ban-all-sheds. I'm sure you wouldn't like to meddle in my field. (I'm a midwife) Regards to all Blodwen

 

[1john]

after recently witnessing child birth in al its gory, i mean glory, no i mean gory, i wouldn't like to meddle in your feild either, good luck with getting it sorted

 

[ban-all-sheds]

I'm sure you wouldn't like to meddle in my field. (I'm a midwife)

Damned right I wouldn't, because I recognise that my ignorance of that field and my subsequent incompetence in it mean that I shouldn't have a go.