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Tim JA
Tim JA, Construction Worker
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I am replacing a bathroom light and noted 6 wires coming

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Hi I am replacing a bathroom light and noted 6 wires coming from the ceiling. 2 green ground wires are clear, 1 red and 1 black are live and neutral, but also 1 blue and 1 brown wires. However when i tested the blue and the brown wires assuming they should be neutral and live under the new colour code, there is no voltage difference between the 2 and they seem to both carry 60volts. what are they please?
JA: Have you replaced the light fixture or switch before? If so, how long ago?
Customer: no I have never replaced this particular one. could have been put in a long time ago by the previous owner
JA: How long has this been going on with your lighting? What have you tried so far?
Customer: i'm trying to replace a light
JA: Anything else we should know to help you best?
Customer: no

Good afternoon, and welcome to the Technical section in JustAnswer, an independent paid question and answer platform that matches customers' questions to experts in various skills. My name is ***** ***** I'll be happy to help you today.

This might take some unpicking, but it's just a case of working through things logically.

First of all, do you happen to have a photo showing how the 6 wires were connected to the previous/existing light fitting?
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There's no time pressure on this topic - it will stay open to you for many days, and you can reply at any time. I will be away from my desk sometimes, but will respond as soon as I can.

You might see automated adverts for phone support. I'm not available for a phone call today, but we can continue via this Q&A topic.

Customer: replied 1 month ago.
Hi sorry I have no picture of what it looked like when the wires were connected to the old light fixture. Wish I took one and I will definitely do next time. But here is a picture of the wires and the new light fixture

Is there a switch for this light fitting?
And does that switch serve just one fitting?

Customer: replied 1 month ago.
The switch serve 3 fittings

Are those other two light fitting coming on when you close the switch?

Customer: replied 1 month ago.
Please see the picture attached. 2 wall lights and 1 ceiling light which is the light in question.
Customer: replied 1 month ago.
File attached (41QLM4L)

They look like lovely dogs :-)

Customer: replied 1 month ago.
Oops sorry
Customer: replied 1 month ago.
currently the other 2 lights do not turn on when I turn the switch
Customer: replied 1 month ago.
I wired the ceiling light in (wrongly) once and when I switched the light on, the switch in the consumer unit which controls lighting on the floor jumped. since then i disconnected all the wiring in the ceiling light. and I haven't check if the wall light bulbs are ok. would you like me to check that?

Yes please. Clearly, you need to stop the 6 wires from touching each other and anything metal and anything human.

Do you have a photo (or notes) showing the connections as they were when the circuit breaker tripped?

Tim JA and other Home Improvement Specialists are ready to help you
Customer: replied 1 month ago.
the wires are all separate and not touching anything. when the circuit breaker tripped the red and the black were connected to live, and the brown and blue were connected to neutral and the green ones to ground. I think I wired it the way it was before, but found it counterintuitive as I would have thought brown and red should go into live and blue and black into neutral due to colour coding.
Customer: replied 1 month ago.
subsequent to the circuit tripped i didn't want to mess with the wires unless I knew for sure which is live and which is neutral, so tested the wires iwth a multi meter, then I encountered the problem of the red and the black show 230v difference, but blue and brown show no voltage difference. and blue and brown both show 60v against the green wire
Customer: replied 1 month ago.
i have now checked the wall light bulbs are functioning

Which wires are you designating as "live" and neutral"?

Is there a fan in the room? Is that working?

BTW, you cannot (and must not) make any assumptions about colours.

Customer: replied 1 month ago.
there is a fan in the room controlled by the same switch and it isnt working
Customer: replied 1 month ago.
the red wire shows 240v against the ground wire and the blackwire so I think it is live
Customer: replied 1 month ago.
the blackwire shows no voltage against the ground so I think it is neutral
Customer: replied 1 month ago.
the blue and brown are confusing, as when i put the multimeter prob on each of them, there is no voltage difference shown between the 2 wires, but if I put the black probe on a ground/green wire, and red probe on either of these 2 wires, it shows about 60v

I suspect the following:

red - incoming live
black - incoming neutral
brown - switched live to fan
blue - I have no idea at the moment

As a next step, I suggest the following:

1. Power off the circuit.
2. Connect the red and black to the live and neutral of the new light fitting.
3. Make the brown and blue safe in spare terminal blocks.
4. Power up and see if the light now works.

Customer: replied 1 month ago.
File attached (G2M47VM)
Customer: replied 1 month ago.
just put it in a table to show what i tried
Customer: replied 1 month ago.
ok will try. the blue and brown i have no terminal blocks for, but i have plastic wire cap and insulation tape
can i use them just keep them out of the way?

Don't use insulating tap - it just makes a gummy mess. A plastic cap will do. Just be careful.

With the power off, could you also check continuity between the two G wires?

(G = green)

Customer: replied 1 month ago.
this is with the power off right? when i test for continuity by touching the red and black probe on the 2 green wires (and i tried swapping the position around) there is no beep and the multimeter still shows 1, so i suppose this means no continuity between the 2 green wires?
Customer: replied 1 month ago.
i have just wired in the black and red liek you said, for the ground wires, should i wire in both the green into ground? or only the one that is showing voltage against the red wire?
Customer: replied 1 month ago.
ok I wired in the red and the black and the green which shows voltage against the red. now the light is working. however it is permanently switched on - aka when i turn the light switch, nothing happens to the wall lights or hte fan, but the ceiling light is just on, and it doesn't switch off.

No don't wire the green wires to ground, as one of them seems not to be an earth.

Please excuse me because I had to make some calls and now have a Zoom meeting until about 9:30pm. I'll post again after that.

Customer: replied 1 month ago.
thanks talk soon

I'm back - sorry for the delay. I'll just digest your latest posts...

OK. So red/black seem to be a permanent supply. That suggests that either brown or blue must be a switched live. So...

1. Power off.
2. Swap red with brown.
3. Power up and test.

Customer: replied 1 month ago.
that doesn't work. the brown is wired into live and red removed. now the light is off permanently
Customer: replied 1 month ago.
when i try to switch on the light, none of the lights go on, neither does the fan switch on.
Customer: replied 1 month ago.
shall i try the blue as the live now?

You might as well do that, yes.
This defying logic at the moment, so while you do that I will re-read your earlier tests.

Customer: replied 1 month ago.
nope. blue in live, black in neutral, nothing turns on

So to double-check...

With all of the 6 wires disconnected, you had control of the wall lights with the switch - is that correct?

Customer: replied 1 month ago.
no. when the ceiling lights wires are all disconnected, the wall lights and fan are both dead
Customer: replied 1 month ago.
i wonder if that means whilst the red powers the light, the blue/brown may be needed to bring power out to the other appliances?

OK I'm confused. At 6:23pm you wrote this:

"i have now checked the wall light bulbs are functioning". Could you confirm that?

Customer: replied 1 month ago.
i checked the bulbs not the wall light fixture
Customer: replied 1 month ago.
sorry I wasn't being clear. in the chat before then you asked me if the light switch works for the wall light. I said no it doesn't but shall i check that the bulb are functioning (not blown out), which I checked - the bulbs are fine.
Customer: replied 1 month ago.
the wall lights are not switching on, and not due to blown bulbs.

OK I completely misinterpreted "the wall light bulbs are functioning".

When was the last time that the wall lights were operational, i.e. actually on, and under control of the switch?

Customer: replied 1 month ago.
right before i changed the ceiling light

OK please bear with me...

At the moment, it seems that the blue and brown might go to the wall lights, and the neutral from those has its own route to the circuit neutral.

If that's true, the 60V measurement is explained by backfeeding of the supply from the neutral of the circuit, through the lamps in the wall lights. If you were to turn off all of the other lights in all other rooms, you might find that this 60V drops to zero. That's a test you can do, but is more difficult at night.

What's unexplained is how the switch is connected. For that reason I suggest powering off and taking a photo of the connections to the rear of the switch.

Customer: replied 1 month ago.
File attached (P5ZZG37)
Customer: replied 1 month ago.
seems like the back of the switch is just connected by blue and brown wires

Hm, do those blue and brown wires have solid core conductors, or stranded?

Customer: replied 1 month ago.
solid. and i don't think the wires in the switch should be broken as the wal light, fan and switch were recently installed by a builder
Customer: replied 1 month ago.
ceiling light has been there since years before though
Customer: replied 1 month ago.
now i have switched the power back on, and turned off all the lights on this floor. the voltage between the ground and the blue and brown have not disappeared and remain c. 60V
Customer: replied 1 month ago.
is there any tests you would like me to re-do? just in case.
Customer: replied 1 month ago.
wonder if i should try red and brown in live, black and blue in neutral?

Two wires at the switch is a common arrangement.

Can you power off that circuit, and measure resistance across the brown and neutral at the light fitting, with the switch (a) open and (b) closed?

I don't think it's a good idea to try random things.

Customer: replied 1 month ago.
OK will try tomorrow morning. Thanks

OK. I'll be around for some of the morning.

Customer: replied 1 month ago.
Morning. Just got a response from the builder who worked on the bathroom and said he wired the wall lights and fan through the ceiling light
Customer: replied 1 month ago.
Not sure if this is useful info
Customer: replied 1 month ago.
the resistence between the brown and blue wire is .05 ish whether the switch is on or off, that's pretty much negligible right?
Customer: replied 1 month ago.
my thoughts are the builder confirmed he wired the other appliances through the ceiling light (believe it's called daisy wired?), hence the blue and the brown may carry no electricity but simply serve as a connection point which bring electricity through the ceiling light into the other appliances. whcih explains why there is no voltage difference between the 2, no voltage difference between them against a ground wire. (but i dont knon why there should be 60v between them against the other ground wire) in that case, should I just connect the brown and the red (live) and blue and the black (neutral)?
Customer: replied 1 month ago.
tried that, seems all appliances are working now. still not sure why the 60volts. could ground wire carry voltage? or the blue/brown wires that connect the ceiling to the other appliance, even though they are disconnected?
Customer: replied 1 month ago.
or do you think that might indicate problem somehwere in the system that we should investigate pls

Good morning! I like your news :-)

To answer your questions...

1. Ground wire
I strongly suspect that one of the green wires isn't a ground. If it's supposed to be, then you have a wiring fault that needs to be looked into.

2. The 60 volt mystery
This could be caused by a "borrowed neutral" from another circuit that still has power. Electricians should not do this, but some do. My general advice is that you should always treat neutral conductors with respect, because MCBs are single-pole. So when the live is isolated, the neutral remains connected to isolate only

Or, it could indicate wiring damaged.

Or, it could indicate a poor connection somewhere.
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In summary, I recommend that you have an EICR carried out at some point. This is a formal inspection by a qualified and registered electrician with full documentation. It will tell you the current state of the important aspects of your installation. If you find a decent and honest electrician, it won't cost you much and is tremendous peace of mind.

Customer: replied 1 month ago.
Thanks Tim

You're welcome; I'm glad that I could be of some help. I hope you enjoyed your experience with JustAnswer.

Have a wonderful day :-)