Changing Light Fixture and now Light Won't go off


Postby Haylz1990 » Sat Mar 18, 2017 10:06 pm

We have changed the light fixture and reconnected it! It's a 2 light switch. However, the light is staying on all the time & wont go off! The original fixture was connected as per first photo I've added! Any ideas at all???
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Postby ericmark » Mon Mar 20, 2017 10:27 am

No photo but this is a regular problem. You will have two or three cables in the ceiling rose, these will be feed in, connection to switch, and maybe feed to next switch.

In the ceiling rose you have an earth clamp and a terminal block split into three, there will be three holes in the centre one, two to one side and three to the other.

The wires which connect to the centre block DO NOT connect to the lamp, these are live all the time as are there for emergency lights and ceiling fans and are not used with normal lighting.

Only the end two and three connector blocks connect to the light, in theory one should be neutral colour the other line colour, in practice often the sleeve has fallen off so both the neutral and line wire is the same colour.

When removing the ceiling rose to fit lights direct there are special junction boxes designed to connect all cables together and leave you with a single three core cable going to the light, or 2 core if classII, often people do simply use connector blocks but the special JB's are better.

If only two cables it is easy, one black to each of the lamp wires, or blue if new colours, and all reds (browns) together and not connected to lamp. In theory if using a screw bulb you should work out which is line and which is neutral and line always goes to centre pin and neutral to screw. But if wrong way around you could get a shock changing bulbs it one when changing, However I would think most people would switch it off to change bulbs, with bayonet it does not matter.

Where there are three cables of the three blacks (blues) two will be neutral and one is line. I once tried to write a truth table as to how to test wires using the lamp to test with, and got thrown off the forum as a result.

So sorry I am not doing it again, you will need to work out which one is line and which pair are neutral yourself.
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Postby kbrownie » Tue Mar 21, 2017 8:34 pm

Yes a picture would help. But I assume by two light switch you mean two lights that come on using the same switch.

If you have replaced the light fittings, then you have mixed up the live lines and the switch lines. Live lines should be in a loop together but not connected directly to live of the fitting, as that is where the switch line goes.
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