Can anyone help with my bathroom light pull chord switch?

Bgy333 · Oct 13, 2022

I’ve got my P16th edition papers in 2006 so not a total beginner (I’m plumber as my trade tbh) but this pull chord bathroom light is not working and if trips the consumer unit .

Basically the old switch broke so I took a photo of the wiring before fitting a new light.

And it doesn’t work.

The brown an red wires are live and the two connect together are live too. I test them with this blue pen tester .

I’m gonna include photos of everything so any help be great thx

Avo Mk8 · Oct 13, 2022

What I would expect at the pull cord position is that the switch would have been between the red and brown wires, the two earth cores properly sleeved and connected to the switch earth terminal (if there is one), and the black and blue wires connected together by a wago or terminal block isolated from everything else.
Then at the light fitting, traditional connections of L, N and E.
Is this how you have tried wiring it?
Your old switch is two way, but it looks like only the two screws on the left side (third photo) have been used- I'm assuming there aren't enough wires for a two way circuit. Is there another switch for this circuit?

Tidying up of wire lengths and sleeving needed!

The above rather rashly assumes wire colours have been used for their traditional purposes.

Also be wary of quirks of pen tester.

Bgy333 · Oct 13, 2022

Avo Mk8 said:
What I would expect at the pull cord position is that the switch would have been between the red and brown wires, the two earth cores properly sleeved and connected to the switch earth terminal (if there is one), and the black and blue wires connected together by a wago or terminal block isolated from everything else.
Then at the light fitting, traditional connections of L, N and E.
Is this how you have tried wiring it?

Tidying up of wire lengths and sleeving needed!

The above rather rashly assumes wire colours have been used for their traditional purposes.

Be wary of quirks of pen tester.

Thanks for replying so fast but that’s what I did the red in common, brown L1, then the Earths to to E box (u can see where it’s been scorched)

I’ve got a traditional multi meter and so which wires would I test with Red and Black pls?

I thought the pen test was a bit crap when the Earth cable would beep the pen after a few secs!

Thsnks in. Advance (if u reply)….!

Avo Mk8 · Oct 13, 2022

Bgy333 said:
Thanks for replying so fast but that’s what I did the red in common, brown L1, then the Earths to to E box (u can see where it’s been scorched)

I’ve got a traditional multi meter and so which wires would I test with Red and Black pls?

I thought the pen test was a bit crap when the Earth cable would beep the pen after a few secs!

Thsnks in. Advance (if u reply)….!

In your movie the black wire looks nicked - did it get trapped somehow? That bit needs cutting off if you have enough cable length.
Firstly what trips in the consumer unit - MCB or RCD or what?

What are the wire colours at the light fitting? (black/red, or blue/brown) - I mean the wire coming out of the ceiling.
If the new fitting is up, with power off you could disconnect switch and check for any short circuit (between L-E or L-N etc)

Sounds like your earth core may not be connected, or with all this bare conductor about, has got trapped and connected to something it shouldn't!

Bgy333 · Oct 13, 2022

Avo Mk8 said:
In your movie the black wire looks nicked - did it get trapped somehow? That bit needs cutting off if you have enough cable length.
Firstly what trips in the consumer unit - MCB or RCD or what?

What are the wire colours at the light fitting? (black/red, or blue/brown) - I mean the wire coming out of the ceiling.
If the new fitting is up, with power off you could disconnect switch and check for any short circuit (between L-E or L-N etc)

Sounds like your earth core may not be connected, or with all this bare conductor about, has got trapped and connected to something it shouldn't!

I’ll take some more photos and post them now

Bgy333 · Oct 13, 2022

more photos
The trip switch is first one on the left

Avo Mk8 · Oct 13, 2022

OK
So I'm sorry but I don't understand what I'm looking at in the multitude of photo's.
The last ceiling fitting in your first post, is not the same as the last photo in the second post of photos (post #6)?
Do you have two seperate ceiling fittings?
The last photo in the #6 post shows two red wires in the ceiling rose. where has that second red wire come from and go to?
I don't see two red wires in any of the other photo's!
Tell me the setup Please!

So it's the MCB on the left of the CU that trips, not the RCB on the very right?
I guess that means you have some sort of short circuit between L & N on this circuit

Bgy333 · Oct 13, 2022

Avo Mk8 said:
OK
So I'm sorry but I don't understand what I'm looking at in the multitude of photo's.
The last ceiling fitting in your first post, is not the same as the last photo in the second post of photos (post #6)?
Do you have two seperate ceiling fittings?
The last photo in the #6 post shows two red wires in the ceiling rose. where has that second red wire come from and go to?
I don't see two red wires in any of the other photo's!
Tell me the setup Please!

So it's the MCB on the left of the CU that trips, not the RCB on the very right?
I guess that means you have some sort of short circuit between L & N on this circuit

I’ve pulled the wires down and cut little bit grey sheathing off.

The other pictures are the light fittings where the wires connect to the lights themselves.

Then a picture of the consumer unit

Hope this helps!

Avo Mk8 · Oct 13, 2022

Bgy333 said:
I’ve pulled the wires down and cut little bit grey sheathing off.

The other pictures are the light fittings where the wires connect to the lights themselves.

Then a picture of the consumer unit

Hope this helps!

Just to clarify - there are two light fittings as well as the switch?
Have you already rewired the ceiling rose shown in the last photo (I mean the photo with the close up of the metal bar), with the two red wires in it?
Presumably you have two red, two black, and two earth feeding that light?

Bgy333 · Oct 14, 2022

Avo Mk8 said:
Just to clarify - there are two light fittings as well as the switch?
Have you already rewired the ceiling rose shown in the last photo (I mean the photo with the close up of the metal bar), with the two red wires in it?
Presumably you have two red, two black, and two earth feeding that light?

That’s a yes to 2 light fixtures

1st one

2 black
2 red
2 earth

2nd one

1black
1ted
1 earth

Avo Mk8 · Oct 14, 2022

Bgy333 said:
That’s a yes to 2 light fixtures

1st one

2 black
2 red
2 earth

2nd one

1black
1ted
1 earth

What I would check first, with power off, is disconnect the red and black at the switch, and with no bulbs in the light fittings, use the multimeter on ohms range, check there is infinite resistance (ie open cicuit) between black and red. Not ideal, but at least would rule out a direct short in this section. Have you done any simple continuity checks to see if any miss connections?

I'm not clear if you have the new lights installed, or if wires are still hanging from the ceiling? Are new lights now in place, or are cables still disconnected?

Avo Mk8 · Oct 14, 2022

Please could you explain the series of events that lead to the breaker tripping?
Did it trip when you first turned the power back on after wiring the lights,
or did you switch the power on, nothing happened, then you pulled the switch cord, and the breaker tripped?
If the second, the pull switch might now be welded permanently on!

Normally one would expect to test a circuit before applying power to it, though that doesn't seem to be the DIY way!

Bgy333 · Oct 14, 2022

Avo Mk8 said:
What I would check first, with power off, is disconnect the red and black at the switch, and with no bulbs in the light fittings, use the multimeter on ohms range, check there is infinite resistance (ie open cicuit) between black and red. Not ideal, but at least would rule out a direct short in this section. Have you done any simple continuity checks to see if any miss connections?

I'm not clear if you have the new lights installed, or if wires are still hanging from the ceiling? Are new lights now in place, or are cables still disconnected?

The lights were installed before (by me) and worked fine, it’s when the old switch was faulty and I’ve gone to install the new one I’ve had problems of it tripping out. I just took a photo of the old wiring and copied it to the new switch

Avo Mk8 · Oct 14, 2022

Bgy333 said:
The lights were installed before (by me) and worked fine, it’s when the old switch was faulty and I’ve gone to install the new one I’ve had problems of it tripping out. I just took a photo of the old wiring and copied it to the new switch

OK I understand better, thanks.
It seems obvious to concentrate on there being something wrong in or around the new switch.
The way you've described wiring it is how I would have done it!

Do the lights work all of the time, and the mcb trips only sometimes, or how does the tripping manifest itself?

davesparks · Oct 14, 2022

What was wrong with the old switch? Could it have been the fault making the old switch appear to be faulty when it actually isn't?

Bgy333 · Oct 14, 2022

Avo Mk8 said:
OK I understand better, thanks.
It seems obvious to concentrate on there being something wrong in or around the new switch.
The way you've described wiring it is how I would have done it!

Do the lights work all of the time, and the mcb trips only sometimes, or how does the tripping manifest itself?

As it is now ( or was when wired as everyone including me assumed was the correct way) it would work for a bit then trip out, I’ve decorated since the dodgy switch started being dodgy and as a typical tradesmen the wife keeps reminding me every f’n year to sort it it and this year seems the year ! So basically recently the lights have been removed and wires hanging down ( it’s fine it’s adults only house!) and the string tied up . When some one not familiar with it would pull the cord it would trip and you have to pull again otherwise it would constantly trip.

Bgy333 · Oct 14, 2022

Tbh it could possibly have been the wiring but I just assumed the switch was broken so replaced it but just coped with no bathroom light for about 4 years lol

Avo Mk8 · Oct 14, 2022

Bgy333 said:
As it is now ( or was when wired as everyone including me assumed was the correct way) it would work for a bit then trip out, I’ve decorated since the dodgy switch started being dodgy and as a typical tradesmen the wife keeps reminding me every f’n year to sort it it and this year seems the year ! So basically recently the lights have been removed and wires hanging down ( it’s fine it’s adults only house!) and the string tied up . When some one not familiar with it would pull the cord it would trip and you have to pull again otherwise it would constantly trip.

Well from everything you've said it seems there has been, and still is, a long standing fault, where if the switch was on, the MCB would trip. That implies somewhere between the light switch and the last light fitting, there is a problem with the wiring. The fact that an MCB trips and not the RCD (assuming the latter works - have you tried the test button recently?) implies to me a more serious problem.
I think either you should get a professional in with a multifunction tester to investigate, or as a minimum, replace the cables in the ceiling with new, all the way from the switch to the first light and then to the second light.

Avo Mk8 · Oct 14, 2022

davesparks said:
What was wrong with the old switch? Could it have been the fault making the old switch appear to be faulty when it actually isn't?

Sounds like you're right!

Bgy333 · Oct 14, 2022

I’ve just got my multi meter in the wires in the loft the blue and brown is showing no reading and the read and black a tiny one I’ll include a pic and show the settings on my multi meter, obv the wires are all dangling so if I’m supposed to be connecting 2 lives I’m not. Cos ones not live and the other minimal

Bgy333 · Oct 14, 2022

photo of the wiring in the loft it leads to this switch

Bgy333 · Oct 14, 2022

So maybe this is where the issue is as there’s only one live wire here and I’m assuming there were 2 lives needed connecting, maybe the switch was being used as some kind of junction box and the switch was thswitch?

The switch isn’t in the bathroom and obv that wiring is new , I’ve discounted that switch as nothing as it “didn’t work”, it’s in a room connecected onto the bathroom by a door and this room was knocked into one massive bedroom before we moved in. I redid the partition and that switch never worked and so that’s where my problem maybe?

Bgy333 · Oct 14, 2022

Whwre the switch is near the door into the bathroom

Avo Mk8 · Oct 14, 2022

Bgy333 said:
photo of the wiring in the loft it leads to this switch

I'm trying to make sense of those first two pics. This seems to be the problem.
the metal clad switch with the red, yellow, blue wires coming out of it seems to be a two way switch to operate the bathroom light in conjunction with the pull cord.
If the brown and blue wires leading off to the left go to your pull cord, then the old (broke) pull cord switch was being used two way. The bare copper earth wire is being used as the common live.
So it's not an earth wire at all!
If you want to continue to use that metal switch in pic 2, then that bit of brown/blue cable in pic 1 needs repacing with 3 core to the light switch. I think the problems you have been having are all because the earth wire is being used as a live wire, and now that is a problem at the new pull switch.
Is your new pull switch 2 way?
Can you replace the 2 core cable with 3 core without too much difficulty?

getting somewhere now !

Avo Mk8 · Oct 14, 2022

Bgy333 said:
I’ve just got my multi meter in the wires in the loft the blue and brown is showing no reading and the read and black a tiny one I’ll include a pic and show the settings on my multi meter, obv the wires are all dangling so if I’m supposed to be connecting 2 lives I’m not. Cos ones not live and the other minimal

In addition to the other recent discoveries, the leakage across red and black just using a multimeter is a bad sign.
You need an insulation resistance tester to check the resistance at 500V. Have you got a friendly sparky who could do that for you?