Submitted by BSPirat t3_z8qfw7 in DIY


So the lightbulb in the master bedroom stopped working. The bulb is fine and the switch is fine. One of the cables on the switch is constantly live and the other will become live when the switch is on. The socket doesn’t show live when the switch is on, so I have removed the lid that is on the ceiling and saw what you can see on the picture. I expected 2 cables there, so this came us a surprise.

  1. What is the name of it?
  2. If I know the name I should be able to find schematics how it’s connected internally but if you have a link for it, this will be helpful.
  3. Without the schematics I can’t understand why the 3 ports in the middle are live even when the switch is off. They are named ‘Loop in’. The ones on the right are named ‘Flex L’ and the ones on the left are ‘Flex N’.

When the switch is on the ‘Flex L’ should become live but it’s not, so it seems there is a problem with the cable between the switch and ‘FlexL’ or internal problem with this thing if it use some kind of a relay or transistor. I would like to find how this is connected internally before I keep go deeper.

This is in England.

Edit: All fixed now. In the morning while I was checking the switch I just took it out and checked the exposed metal parts where the cables go in. This is how I determined the switch was working. However I didn’t check for loose cables and as suggested this is where I started. One of the cables was loose. Now it’s back on and tightened and the lamp works again.



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Acceptable-Fox-4341 t1_iycrv4k wrote

Not an electrician but have been doing up my old house....

  1. Lights here in the UK are usually on a "loop in system". So there is power flowing through the loop even if the specific light fixture is off. The plastic part with the connections is known as a ceiling rose

Behind the plastic should be three cables. One coming from the prior light fixture, one Going to the next, and one to the switch.

There needs to be a circuit at all times even if your light is off... Otherwise the switch would turn off all the lights down the line.

The middle three should be all the lives. The flex N should be the two neutrals from the loop and the neutral from the light fitting. The remaining two should be the switched live (black with red tape) and the live going to the fitting.

At a glance it looks like it's wired correctly. Id assume it's probably the light fitting or ceiling rose at fault. You can get a new one for less than a fiver.


usernameandnumbers t1_iyd02r7 wrote

I had this exact issue and couldn’t work out why my light wouldn’t work, it was the living room light and it turned out the kitchen wiring wasn’t correct so electric wasn’t “flowing” into the living room.

OP check the wiring of your other lights on the same floor


BSPirat OP t1_iydbak7 wrote

Everything else works except of this one. And as I mentioned I don’t have anything on the Flex L side, so the issue is in the cable that comes from the switch to the lamp - the black one with red sleeve.


generationgav t1_iydj47x wrote

>Without the schematics I can’t understand why the 3 ports in the middle are live even when the switch is off. They are named ‘Loop in’. The ones on the right are named ‘Flex L’ and the ones on the left are ‘Flex N’.

Change your switch first, I had an issue with mine I couldn't work out and it turns out the switch had broken itself.


ToolMeister t1_iydnjt9 wrote

OP says switch works as designed


generationgav t1_iydnt70 wrote

Yes - so they did.

If it's live going into the wire and not live coming out of the wire (so to speak) then sounds like a break in the wire.


ToolMeister t1_iydo4l3 wrote

Check all connections (breaker off), pull on the wires to see if anything is loose.

The hot wire of your fixture (brown) doesn't seem to get power from the switched hot of your switch (red sleeved black).

If you ruled that out, measure continuity between the switch and the fixture to see if the wire is broken somewhere


Just_wanna_talk t1_iyd7dnj wrote

What's the benefit of this "loop in" system? It seems quite complicated, possibly dangerous, and requires more hardware than a simpler system that we use in north america.


kilrcola t1_iyd7rvz wrote

It uses less cable initially. We use loop at the switch now because often lighting switches have an led indicator which needs a neutral and also ease of adding other circuits off the switch.

Loop at the light is the old way here but it's still pretty common in Australia as it only requires two cables per switch group, the new way has S N E for each load. More cables.


kilrcola t1_iyd4q4a wrote

Electrician here from Australia. Different standards but the concept is the same.

I should preface this with, Electrical work can be dangerous especially if you don't have a residual current device to protect you. A circuit breaker protects the cables and a RCD protects us. Call a professional if you don't feel confident.

Be sure to isolate and turn off your mains or individual circuits. Use a volt stick and a meter and check for dead and also on a known power source and then recheck for dead.

Now to the wiring.

It sounds like you have something called 'loop at the light's'

Basically you have a permanent active, neutral and an earth that is ran around the house to each light fitting. Then you have two cables down to the switch, one connected to the permanent active and the other connected to the switch active of the light fitting. Typically in Australia this is white = switch wire and red = permanent active (but not always)

If your light fitting is in the centre of the house it will have an in and an out for each of the cables as it loops from the last room into the next room.

It looks like the fitting neutral on the left is the blue, the two blacks next to that are the incoming and outgoing neutrals, the two Red's next to that are 'probably' the permanent actives, the next two are probably red permanent and in this case black switch wire (maybe), then you've got the fitting switch active on the far right, which is linked internally in the fitting to the switch active down to the switch.

You'll need to test it (I can't stress this enough), as the picture isn't that clear but that is what makes sense to me that the neutrals and permanent actives (are each seperately) in a linked bar inside the fitting.

You're also relying on the fact that someone has wired it correctly beforehand. I find heaps of wiring that they use the black cable as permanent active or blacktive as we call it, which should never be done.

You've also got solid copper wiring N and L so be careful not to over tighten and crush the copper in the fitting as this is how the copper strands snaps. We usually double over and fit it off for this reason in case of breakages it has a redundancy.

Flex means flexible cable btw. N means Neutral and L means Line which is Permanent active. Switch can be SW or SA.

Goodluck and I hope I have explained it well enough to make some sort of sense.

Edit: I re read your problem. I'd check for single copper breakages in the fitting as I've listed above. Basically pull each cable out one by one and replace it and check each strand is not broken. (With the mains off).

Here's an image which may help you understand what's going on:


rfc2549-withQOS t1_iydwudp wrote

Just to add colouring: EU colour codes say blue is neutral, Black is line and the orange is switched L

I'd try getting a reading with a tester to make sure of the colors, though (red was used for earth aeons ago, for example)


kilrcola t1_iyemuht wrote

Always, always, test. This is rule 2. Right after isolating once you know what's what. 🤠


64b0r t1_iyctnjt wrote

Don't wanna be a wiseass, but you need a lightbulb moment, my friend.


BSPirat OP t1_iycuhxt wrote

Hopefully my internet wiring and bulb have no problems 🤣


MINKIN2 t1_iydn2k5 wrote

Okay, as we are doing this...

Have you tried turning it off and on again?


lightknight7777 t1_iyda83o wrote

Huh, that looks even more complicated than an American thermostat. Good luck, I'm very competent at our two wire system but that many cables for a basic light would drive me nuts. Too many points of failure.

I would still try to make sure all the wires are still actually in the contacts (might be loose or broken in one). If your systems run through multiple sockets and lamps, I'd make sure other ones are still functioning too. For example, I once had a full wall go down and found the problem was the head of a wire snapped off inside a wall outlet so the connection was cut to all other objects on the breaker.


BSPirat OP t1_iydca3d wrote

Thanks to @Acceptable-Fox-4341 I now know how it works. Not so complicated as you see what is going on. All other lights on this level are working properly. My issue seems to be with the cable that comes from the switch to this rose.


rvgoingtohavefun t1_iydhgjd wrote

This type of wiring is actually quite common in older homes in the US as well and is why smart switches say "neutral required." There isn't always a neutral at the switch, depending on how it was wired.

You can run the power to the switch (neutral, hot, ground) switch the hot, and then run the neutral, switched hot, and ground to the fixture. This is probably what you're accustomed to.

You can run the power to the fixture, then run a 3 conductor (plus ground) cable to the switch. The white is unused for a standard switch. Black is hot, red is the output of the switch.

In the bad old days, you could run the power to the fixture, then run a 2 conductor (plus ground) cable to the switch and just switch the hot off and on. Assuming black/white conductors, the black is hot, the white is the output of the switch. There is no neutral at the switch. This is not allowed by code any longer. This is more or less what you see here.

In the picture, you can see there are three groups of screw terminals. The wires within each group are connected internally by that plate.

The left group (blue, two blacks) is the neutral, continuing the circuit for the next fixture (black) and connecting to the lamp (blue).

The middle group (red) is the hot.

The right group (black, brown) is the return from the switch.

In this setup, replacing the fixture just requires undoing the screws for blue and brown, removing the wires under them, putting the wires for the new fixture in the newly opened slots, and tightening the screws. It's no more complicated than anything you'd see in the US, arguably less so than anything involving wirenuts, especially if the power goes to the fixture first.


lightknight7777 t1_iydnvd2 wrote

>arguably less so than anything involving wirenuts

I've taken to just wiring plugs at the end of wires so I will be able to just wire the male plug into new appliances I intend to replace old ones and just plug them in once it is time. So much easier to do that on the ground than have to deal with twisting those wirenuts at the top of a ladder. But these are for home and family/friends where I don't mind spending an extra $4 for future proofing. It's also a lot easier than installing a whole new outlet for things like garbage disposals where the person accidentally got a plug version so I don't have to worry about stripping the cabling and taping up the connections out in the open where water can be a problem.

EDIT: Apparently what I meant wasn't understood. I'm just converting the ends of the cables from a hardwired version to a plugged version. The female is always secured and it lets the appliance just plug directly into it. This is literally no different than it being a plugged appliance unless anyone knows any better. Plugs aren't special, they're just hardwired into the plug rather than directly into the junction box by way of wire nuts connectors or wago connectors.


rvgoingtohavefun t1_iye0h7z wrote

I'm fairly certain what you're describing isn't legal at all.

It's supposed to be a secure mechanical connection. A plug that can pull itself apart sure isn't a secure mechanical connection. You may also be overfilling the box, which is a fire hazard in its own right. You can get arcing or excess heat (without excess current draw) which could cause a fire without ever actually tripping the breaker.


lightknight7777 t1_iye5mlk wrote

If you plug a cable into an outlet it can pull out exactly the same. The female connector is always secured to the back wall and is no different than an outlet being there. And the appliance is firmly connected into the male plug hardware. I'm just converting the appliance to a plugged appliance.

Am I not explaining something correctly? The only thing you have to know is that the plugs are the right spec. Like you wouldn't grab 220V plug adapters. It's literally like running an appliance to an outlet. I'm not talking about cramming anything into a cramped space.

What are you imagining I'm saying? Do you have any kind of example?

Like for example, let's take it to the most extreme possibility of just converting random things into plug versions, are you saying the following would be dangerous/illegal (the guy doesn't use a polarized plug like he should and is the epitome of a beginner, but I'm talking about the concept):

The wires are secured into the plug. The plug coming unplugged wouldn't do any damage besides cutting the power. Really curious what you were thinking about.


rvgoingtohavefun t1_iyefwf2 wrote

We're talking about light fixtures, here, or, at least, I thought we were. You said "deal with twisting those wirenuts at the top of a ladder", and most appliances (other than light fixtures, which I assumed you were referring to) aren't installed in a location that requires a ladder.

That first video is installing a stove/oven plug or dryer plug or something. I didn't really watch it. I'm not sure what you're getting at with that.

The second video is installing a fixture (that already uses flexible lamp cord) and plugging it into an extension cord (note that using an extension cord for permanently-installed fixtures is also not allowed, but that's not what we're talking about anyway).

We were talking about things that otherwise required wire nuts and were at the top of a ladder, so I presumed we were talking about normal light fixtures.

If you're putting a female end on the wires up in the ceiling and burying it INSIDE a junction box, that's not allowed.


lightknight7777 t1_iyegi3c wrote

That's a lot of assumptions.

I'd be absolutely fascinated to know how you thought there being a plug there could cause an arc that would then somehow not short the breaker in a way that a wire nut would. From an electrical perspective, there's virtually no difference between a male to female plug connection and a wire nut.


Westerdutch t1_iydanfh wrote

> So the lightbulb in the master bedroom stopped working.

Any idea what caused it to stop working? If nothing changed theres no real reason for it to break.


thetinsnail t1_iydbelq wrote

Exactly this. I want to know everything that happened between the lights working correctly and now.


Westerdutch t1_iydd1wu wrote

Yup, tearing your house apart should never be step one. Other than the bulb there are not a whole lot of things here that can randomly break. Someone changed something, that change is the prime suspect and not everything else that always worked fine.


BSPirat OP t1_iydd3e4 wrote

Have no idea. My wife switched it on and it turned on but flickered for a bit and switched off. No changes have been made and this is the only one that doesn’t work. I already have a good idea what is the cable with the issue. After I confirm it’s the problematic one and find what has happened with it, most probably I will find out why it happened.


Westerdutch t1_iyde5s6 wrote

A cable failing would be a weird one... Hope its something obvious like a rodent eating through something because if the wiring in the walls of your house are capable of spontaneous failure like that you will have much larger problems than one bulb not turning on.


tiredofmakingshelves t1_iyddhmc wrote

It's in the UK, so start of winter. I'd bet either a mouse has moved in and chewed through a cable in the attic, or there was an old damaged cable in the wall with a screw through it and slight house movements due to temperature have moved damaged cable ends apart.


Westerdutch t1_iydeyx0 wrote

> either a mouse

Yeah thats what i thought too. I just hope for OP that this is not a case of aluminium wiring deciding to give out because that would indicate a much wider issue but i dont think that was ever an issue in the UK (they did that weird ring mains thing to save on copper iirc).


tiredofmakingshelves t1_iydd5wf wrote

How do you know the switch is fine?

WITH THE POWER OFF: At the light, check continuity between the switch wires (test between the block of reds, and the black next to the brown). You should get continuity with the switch on, and no continuity with the switch off. If you don't get any continuity, then short the wires at the switch (can put them both in the same switch terminal) and retry. If you start getting continuity, replace the switch. If still nothing, you have a broken wire between the rose and the switch.

If you have a broken wire between rose and switch, there's probably a screw through it somewhere - check for pictures mounted above the switch. Replacing cables is a right pain - if you have attic access follow the wire up there and check for damage. If you're super lucky the fault is in the attic and you can replace a section (with an attic-accessible junction box) without damaging walls.


BSPirat OP t1_iyde2nr wrote

I checked the switch. When it’s off only one of the cables is live, when it’s one both cables are live. I suspect the cable that goes out of the switch back to the rose is the problematic one but will check this later and if this is the case I will start from the attic.


iksbob t1_iydg236 wrote

Based purely on the labeling and hole spacing, they're giving you 3 terminal strips, plus one for ground.

The reason for the strips is that combining stranded wire and solid wire in a single connector (whether screw-type or wire nut) can be precarious. The solid wire can provide much more mechanical support, making the connection feel tight while the stranded wire can still slip out or is poorly connected.

Back to the fixture plate, under "FLEX N" you have 3 ports ganged together. This should be the neutral/return wire of your lighting circuit/loop - the wire returning to your breaker (or previous light fixture), a wire returning from the next light fixture, and the neutral/return of your light.

Next is "LOOP IN" with 3 ports that should be connected to each other but not the first 3 "N" ports. This is the hot/supply/live/line wire of your lighting circuit. The 3 ports should be: power supplied from your breaker, power out to your next fixture, and constant power out to your light switch.

The final 2 "FLEX L" ports (again, connected to each other but none of the previous 6 ports) should be switched hot/line returning from the wall switch, and the light fixture's hot/line wire.

All together, the strip accepts the power connections from the breaker or previous light fixture on the circuit/loop (2 solid wires), the next fixture on the circuit/loop (2 solid wires), the wires to the wall switch (2 solid wires), and the wires to the light fixture (2 stranded wires).

An observation: the left-most red wire on the terminal strip looks like it gets skinny a cm or two from the strip. It could just be bending behind the black wire (which has a speck of white paint or something on it), or the wire could be broken inside the insulation. If it's skinny, give it a wiggle and see if it bends easily at the thin spot.


mr78rpm t1_iydo9ul wrote

  1. Take all safety precautions. If you get a shock, call an electrician.

  2. Did it ever work?

  3. If so, what changed? Where? In what way?

  4. It's not a bulb. It's most likely called a fixture, or some other name indicating that several things are wired together.

  5. Contact the fixture's manufacturer, if possible, for instructions. Instructions will show you what voltages and connections you should find.

  6. Do you have two more of these things in the house? If you do, you can use a voltmeter to compare how/if those connections compare to your problem.


MINKIN2 t1_iydpn2e wrote

This might sound daft but hear me out? That room doesn't have its own circuit breaker does it?

Looking at that ceiling makes me think that you live in a rather old house(?). Before modern standardisation was introduced, a lot of old wiring was a hodgepodge of random wires going to some individual rooms, and later on when it came to "modernisation", it was easier to just re-trace old wiring paths for particular rooms rather that ripping the walls out for a complete job.


ahoy_fiji t1_iydpoy7 wrote

Have you tried sticking your finger in to see if has power?


LordBiscuits t1_iyduiq2 wrote

The issue is more likely to be in the bayonet fitting you put the lamp into than in the wiring on the harness plate.

Not being funny here, but you clearly don't know what you're doing, so don't fuck with it. Get it wrong and you'll melt shit or seriously hurt yourself.

Go online and find an NICEIC registered electrician near you and ask them to come fix it for you


chaykota t1_iye4ww9 wrote

Electrician here. It looks to me like the neutrals (blacks on the left with the blue flex to the pendant) have come out and need re-terminating, the switch would be live and operate as normal but the light needs a neutral to work. The only problem would be that op said no other lights had stopped working, as this isn't end of line (last light on the circuit) the neutrals not being connected would effect any other light further down the circuit. Test between the earth and switched line (the black with red sleeving connected to the brown) And check for voltage, then check between the neutral and switched line. If all reads 230v the problem will be in the lamp holder (the bit the bulb goes into) if you don't get 230v between switched line and neutral (possibly 115v or something similar) check between neutral and earth if you have 230v between the 2 you have a neutral missing.(just to be clear neutral is a live cable) If you don't have 230v between switched line and earth the cable between the switch and pendant is probably damaged or poorly terminated in the switch. But in all honesty, I recommend contacting an electrician. The equipment you're using to test could be dangerous and not fit for testing this type of voltage. And please do not use the little clear screwdrivers with a light on top, they definitely are dangerous!


chaykota t1_iye79bo wrote

But it most likely is the neutral in the lamp holder, buy a new pendant and switch. Turn off the power, remove the blue and brown flex but leave the rose and all other wiring in place, take the pendant off the rose of the new light and connect the blue and brown into same terminals as before (you'll need slide the old rose cover over the new pendant flex 1st) and change the switch. If that doesn't work definitely contact an electrician.


Warlord68 t1_iycxhu0 wrote

Don’t play with electricity, Hire a professional.


ThatsMrDickfaceToYou t1_iyd1eok wrote

What? This is a simple home repair. Damn, people these days are so happy to be incapable.


Warlord68 t1_iyd1wmu wrote

“One wire is live and the other becomes live when the switch is turned on” this person doesn’t understand basic current flow. Not everyone should do home repairs.


TexasTornadoTime t1_iyd36hg wrote

At worst they get a very minor shock… while electricity is dangerous it is very very hard to seriously injure yourself messing with the wires at this point. Only if you both have a serious heart condition and touch it in such a way that caused that electricity to travel past your heart just right. Both not likely.

Redditors get too fixated on safety rather than help solve the problem. It’s r/DIY not ‘r/callaprofessional’

If you’re that concerned for safety, educate on what they need to do to protect themselves rather than just say call a professional. Defeats the whole purpose of the sub.


dorsalispedis t1_iyd7w7z wrote

While I agree people can be taught to work on their home in a safe manner without calling a professional, it’s dangerous to say that getting shocked is essentially not dangerous (at worst they get a very minor shock). You don’t have to have a heart condition for this to seriously hurt or kill you. Of course, most people that get shocked don’t get seriously injured, otherwise I’d have a lot more electrical injuries in the ER, but that doesn’t mean you shouldn’t treat residential electrical as something that can kill you.


TexasTornadoTime t1_iydcilt wrote

Okay sure but my point still stands this sub is diy not call a professional. More effort needs to be placed on that and how to work safely rather than just say pawn off the job.


relephants t1_iydjf6z wrote

This is a perfect description for UK lightning as its a loop at the light. One wire is always live and the other is controlled by the switch.

So tell us, what was wrong with his description?