DIY Doctor UK DIY Forums

Good afternoon all,

I am having a little trouble fitting a new light fitting to replace an old ceiling rose. The wiring in my flat is all old (black and red), but I have changed a few so far and all been fairly straight forward. However I've come to the last room and there are two of each wire (black, red and earth) rather than one in all the other rooms. I'm unsure which cable should go where, am I right in thinking one of the black wires is the switch live? If so is there a way I can work out which one it is?

Thanks for your help in advance.

You can either follow the cable run to see which one goes to the switch or use a multi meter.
If you haven't got a multi meter why not, do you use a knife to turn screws? You always use the correct tool for the job in this case you need a multi meter. (One can be had for less than £10)

Thanks Mr White. One like this?

https://www.screwfix.com/p/lap-mas830b- ... 0wod8WcPaw

My other question being, once I have identified the switched live, how would the old wiring be arranged in to that new fitting?

Would I be right in saying the black switched live would connect to the brown live wire? Other black neutral to blue. Then earth to earth, then connect the red live wires together separately? Like pic below?

Thanks Mr White. I thought that was what I would have to do. Like one of these?

https://www.screwfix.com/p/lap-mas830b- ... 0wodroEGMg

Once identified, does the switch live go to the neutral on the new fitting, as below?

The meter you have linked to will be acceptable for the task you need to do. Lots of tutorials on youtube. You will soon wonder how you did with out it.

Yes the diagram is correct.

As you seem to have worked out, last one is easy, red to red and one black is neutral the other is switched line. With bayonet bulbs no real problem. With screw bulbs the centre pin needs to be line and screw neutral so some testing is required.

Thanks guys, now to buy and work out how to use a multimeter!

As I have said, there are lots of tutorials on YouTube. But "practice" elsewhere first, as electricity has no prejudices, it kills anyone.