Lighting Circuit Problem

[yartin]

Hi
A friend of mine has a problem with 2 lights not working in the house, she said tried to change bulbs, both flickered and stopped working. There is a 2 gang switch controlling the lights. Other lights on same mcb are working. One light is in a hallway with ceiling rose and the second is an outdoor PIR light.

1. What could be the cause for both lights stop working same time?
2. I had a look at the wiring of the light switch, pls see photo, how does the wiring work?
3. Am I right to say black & blue are the neutral? I tested voltages between the 4 switch terminals and (black and blue) and all were Zero. I thought there should be 240V at the two looped terminals.

TIA

 

[Taylortwocities]

What could be the cause for both lights stop working same time?

Could be all sorts of things

I had a look at the wiring of the light switch, pls see photo, how does the wiring work

This is very basic. The red at the bottom is the live in to the switch. It is looped to the second half of the switch.
The yellow and red at the top of the two switches are the switched outputs to the two lights.

Am I right to say black & blue are the neutral? I tested voltages between the 4 switch terminals and (black and blue) and all were Zero. I thought there should be 240V at the two looped terminals.

Correct. I guess you are using a volt test meter? Have you checked that this does actually work - use a known supply?.
Many people have been fooled by using a faulty tester.

If there really is no voltage beteewn the neutral and the live, then you'll need to find where the incoming live and neutral comes from.
Lots of detective work, I'm afraid.

 

[ericmark]

Am I right to say black & blue are the neutral?

No, phase colours were red, yellow, blue and black for neutral, across the channel was Brown and two blacks for phase colours, but we both changed to brown, black and grey for phase colours and blue for neutral.

Using twin red or twin brown, not easy to trace wires, so in the main switches feed with red/black or brown/blue both being line.

So the only colours which are reserved for one use only, are green/yellow which is for earth bonding, and even that plumbers have been known to use them as a line.

Over the years I have been surprised to see how many loose wires can work for so long before problems manifest themselves. Opening up a ceiling rose and giving each wire a tug, seems all to common to find a loose one.

Today our test gear is so much easier to use, I remember the old days with long leads to test with, today we have even non contact testers which can detect a line cable without even touching the device, showing here how far away from the extension sockets, it could detect voltage, it makes testing so much faster.

But we still need to know how and when to use the different functions.

I tested voltages between the 4 switch terminals and (black and blue) and all were Zero. I thought there should be 240V at the two looped terminals.

In the main with a wired tester I test to earth, as can't be sure what other wires are.

 

[Murdochcat]

I would look at the neutrals

 

[SUNRAY]

Also measure the voltage between the earth terminal in the back box and all other wires