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

6268fcdf-fae4-4c7d-a285-6d1fcd82dc2a.JPG (106.38 KiB) Viewed 213 times

[Someone-Else]

If both lights flickered I would guess there is a loose connection, where, you guess first. (But I would look for where the oustside light comes inside, looking for a junction box)

In this case I would say that the black is going to one light, and the blue is from the supply.
If that is true, the yellow will be the switched live to the other light (Hall?)
It looks like the red that loops from switch to switch is the live supply, you could check between the "double red" (bottom right of switch) to neutral, or to earth.

Has any work been done recenlty, or anything heavy moved?

What are you using to test for voltage?

Believe it or not, there is no colour code for wiring lights in the UK, it is up to who ever wired it, what colour they used for what.

[yartin]

There was no junction box on walls.

I use multimeter.

The red or brown usually (or even always) is (or must be) Live.

She had a builder who fit the PIR 4 years ago, she says he may have changed the wiring at the switch, not a sure thing. No works since.

I think what you say black and blue are live?

Where to find a loose connection?! I guess first check for L connections? The hall light has a ceiling rose, the light fitting part where the bulb sits is loose, I tried to see the wiring there but couldn't take the shade off to start with because the plastic nut was stuck and didn't want to force it, would a loose connection in that ceiling rose be the cause?

[Someone-Else]

There was no junction box on walls.

I never said walls. It could be in the ceiling. Have a look upstairs, see if a floor board has been lifted.

The red or brown usually (or even always) is (or must be) Live.

Not true, as I said it depends on how who wired it what colours they chose to use.

I think what you say black and blue are live?

You think wrong, I never said black and or blue are live.

would a loose connection in that ceiling rose be the cause?

It could be, if that is where the supply is coming from.

Your problem is, you have no idea where the problem is, and sadly, there is no miracle solution other than to trace cables and look for loose connections, no matter how long it takes. But never get flustered, you will often make a mistake. Oh and I would not rely on a multi meter for mains testing, see my signature.

[yartin]

In this case I would say that the black is going to one light, and the blue is from the supply.
What are you using to test for voltage?

There are 3 terminal blocks at ceiling roses, namely Neutral, Loop and Line. I don't know what you mean "the blue from the supply".
Multimeter is fine when on right setting and tested from known working source. I am electrical engineer 90s graduate not an electrician, we use voltmeters and oscilloscopes... TBH I like to see real values not lights flashing.
I still think blue & black link is neutral.
Anyways, the wiring in the switches were working before, the fault now requires tracing to find a loose connection or broken wire.

[Neelix]

I’d be checking the neutrals

[OnlyMe]

This is a wiring setup I do see now and again. Your friend has what is called loop in loop out wiring but has a small variation on it. The black and blue are almost certainly neutrals. The yellow is the switched live to the hallway light and the top right red is the switched live to the porch light.

I would be temped to take down the hallway light and check the connections behind that.