Switching issues on lighting circuit

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Hi,

I had an issue with a lighting circuit a few weeks ago, the detail of which I don’t think will help here. I thought the issue was fully sorted, but this week I noticed that certain combinations of lights are not working as expected.

In terms of my knowledge/experience, I am confident to change light fittings and switches when its like for like, but I’m certainly no electrician.

The circuit has 7 lights on it. I think 3 can be ignored as they were not touched during my recent issue and they continue to work as expected.

Of the other 4, Light 1 is on a 2-way switch (there is also an intermediate involved, but that hasn’t been touched and works as expected), Lights 2,3 and 4 are on 1-way switches.

During my recent incident I had to call in an electrician who removed Lights 1 and 2 to carry out some tests. He left me with instructions on how to rewire the fittings. Lights 3 and 4 were not touched.

I understand that in terms of the ordering of the lights on the circuit, that Light 1 is earliest, Light 1 feeds Light 2, and then 3 and 4 are after 2 (but I’m not sure which order 3 and 4 are in are in). I assume that the other 3 I am ignoring must be before Light 1.

My current situation is that Light1 works as I would expect. The symptoms of the problem can be seen on Lights 2, 3 and 4.

When light 2 is switched on, lights 3 and 4 cannot be switched on (if you switch light 3/4 on whilst light 2 is on, then turn off light 2, light 3/4 will come on). If Light 2 is off, Lights 3 and 4 can both be switched on, but if they are both switched on at the same time, one of the lights (always the same one) is dimmer than if its on on its own.

I assume that during my recent incident Light 1 or Light 2 has been wired incorrectly.

If I take down Light 2, there are 3 sets of wires (each containing their own red, black and earth wires). All the reds are connected to eachother. Of the 3 blacks, 2 are live when tested with a light up pen (this surprised me, based on previous experience, I would have expected to only see one live). Flicking the switch for Light 2 does not stop either being live (and also does not change the other black on – its stays non-live). Both live black wires are connected to the blue wire that comes from the light fitting, the single non-live black wire, is connected to the brown wire from the light fitting. (I tried connecting the 2 live ones to brown and the other to blue, that only changed Light 2 being on when the switch was in the off position and off when in the one position, Lights 3 and 4 behaved the same).

If I take down Light 1 (2-way with an intermediate) I again have 3 sets of wires each containing red, black and earth, but then also 2 single black wires (coated in grey – I’ll refer to those as grey wires from here on). All reds and one of the greys are connected. The other grey (which I think is the permanent live) is connected to the brown wire of the light fitting. All 3 blacks are connected with the blue. If I disconnect these blacks, I see that one is live. If I then disconnect Light 2, it stops being live (so I assume that is the wire connecting Light 1 and Light 2).

Based on the above, does anybody have any idea what can be the issue? Any advice gratefully received, but either way thanks for even reading this far!
 
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It does seem some errors in wiring, it is possible one could do a truth table to work out what has gone on, but in the main easier to simply test.

It seems likely neutrals and lines have been mixed up, so to work out if direct feed the voltage must tested, I know my non contact voltage tester does show four levels, but even that is not good enough.

Measuring voltage to earth should show if on neutral or line side of the loop, but even on sight with my tester it would still not be easy to work out where the fault is.
 
Thanks for the reply, really appreciate you taking the time to read, think and respond. I don't have the tools to test voltage and not sure exactly what I'd be looking for.

I will have a play at switching a few live/neutrals. I assume I won't damage anything doing that?

If anyone could suggest if either fitting might be more likely to be the cause or suggest any specifics to try first that would be helpful. Not sure how possible that is based on just a description though.

Thanks again to anyone who takes any time to think about this. Always blown away by people's willingness to help on this site.
 
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If I take down Light 2, there are 3 sets of wires (each containing their own red, black and earth wires). All the reds are connected to eachother. Of the 3 blacks, 2 are live when tested with a light up pen (this surprised me, based on previous experience, I would have expected to only see one live). Flicking the switch for Light 2 does not stop either being live (and also does not change the other black on – its stays non-live).

One of the ones that is showing as live is the switch live from the switch, the other is the neutral from lights 3, 4, which is reading as live because its got a load on it and is open circuit. You need to work out which is which, with the cirucit off, do a continuity test between each black in question and the reds, one should have continuity only when switch is on, the other will probably all the time (unless you take the lamps out of 3/4)

Both live black wires are connected to the blue wire that comes from the light fitting
Thhats wrong, you want both neutrals there, one of which will be showing up dead on the volt pen, and the one that goes to 3/4 that you are going to identify by elimination by finding the switch wire.


the single non-live black wire, is connected to the brown wire from the light fitting.

No, thats your neutral, that goes with the blues (see above), you want the switch wire to brown, and you should ID it with a bit of red or brown tape
 
One of the ones that is showing as live is the switch live from the switch, the other is the neutral from lights 3, 4, which is reading as live because its got a load on it and is open circuit. You need to work out which is which, with the cirucit off, do a continuity test between each black in question and the reds, one should have continuity only when switch is on, the other will probably all the time (unless you take the lamps out of 3/4)


Thhats wrong, you want both neutrals there, one of which will be showing up dead on the volt pen, and the one that goes to 3/4 that you are going to identify by elimination by finding the switch wire.




No, thats your neutral, that goes with the blues (see above), you want the switch wire to brown, and you should ID it with a bit of red or brown tape

Thanks Adam, this is really helpful.

I'm pretty sure I know which of the two lives are from my switch as the spark that came round labelled it as such when he did the tests you suggest.

He marked the one that is currently neutral as the "feed" from what you suggest this will be the one from Light 1.

So if I know which each of the 3 wires are (from Light 1), (switch) and (to Lights 3/4), I think you are saying that one should be linked to the brown on the light fitting and the other 2 to blue.

Which should go to brown, (switch) or (to Lights 3/4). I would guess (switch)?
 
1700330433964.png

 
Thanks, I was just thinking it through in my head and the above diagram confirms my thinking. I think I know what I need to do.

Massive thanks, in particular to Adam, to anyone who looked at this. You have not only helped solve my problem, but also helped me learn. Makes the struggle to get there worth it.
 

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