Light switch only works when one is on.

All electrical lighting questions in here please. Including outside lighting and light switch / dimmer questions.

Moderator: Moderators

SquirrelHammer
Newly registered Member
Posts: 66
Joined: Mon Dec 04, 2017 9:59 pm
Has thanked: 4 times
Been thanked: 0

Light switch only works when one is on.

Post by SquirrelHammer »

Hi all, .

One light switch (bottom of stairs) needs to remain on for the other (top of stairs) to work, if bottom of stairs light switch is off top of stairs switch does not work.

1 light fitting (chained recessed lights) 2 switches.

Light fitting is connected up by taking a feed from another light into a JB, the JB then has the light fittings all chained up with a typical light switch setup to ONE switch. The one switch does not have any wire going to the second light switch and i cannot see or find out how the second switch is connected up or interacts with the upstairs light fitting.

Any ideas how this voodoo might work?

All other lights in house work fine when the downstairs light switch is off.

Bottom light switch is 2 gang 2 way with 3 cables (t+e). Worse case would be to rewire the hallway which i am avoiding as i would also channel out the light switches as i am fairly sure the wires are plastered in without any protection.
User avatar
Dave54
Senior Member
Posts: 4504
Joined: Wed Feb 25, 2015 7:20 pm
Has thanked: 1128 times
Been thanked: 1037 times

Re: Light switch only works when one is on.

Post by Dave54 »

Ktuludays
Senior Member
Posts: 867
Joined: Mon Oct 27, 2008 11:23 am
Location: Dronfield
Has thanked: 233 times
Been thanked: 200 times

Re: Light switch only works when one is on.

Post by Ktuludays »

It'll be incorrectly wired. Look up 2 way lighting. 4 cores are required to allow correct functionality.

Dave54 beat me to it.

Sent from my HUAWEI VNS-L31 using Tapatalk
Last edited by Ktuludays on Sat Nov 10, 2018 5:58 pm, edited 1 time in total.
If the lessons of history teach us anything it is that nobody learns the lessons that history teaches us.
User avatar
someone-else
Senior Member
Posts: 10309
Joined: Sat Sep 01, 2012 6:03 pm
Has thanked: 24 times
Been thanked: 1757 times

Re: Light switch only works when one is on.

Post by someone-else »

has it always been like this or what has been done recently?
Fret not, a forum is a collection of opinions. Above, are mine.


Working on anything electrical? have you got a multi meter? why not? Would you hit a nail with a shoe?

If gloom had a voice, it would be me. :mrgreen:

:idea1: How to post a picture on this forum Click here

Video of how to resize / rotate pictures can be found on This page
SquirrelHammer
Newly registered Member
Posts: 66
Joined: Mon Dec 04, 2017 9:59 pm
Has thanked: 4 times
Been thanked: 0

Re: Light switch only works when one is on.

Post by SquirrelHammer »

Thanks Dave, yes i know how to wire a 2 way switch you can also wire it via one switch power and the other switch to light fitting but the light switches do not connect to one another and i cannot seem to find out how it connects to the light fitting.

I am sure of upstairs wiring as they had two switches to control the recessed lights upstairs, i removed one switch and chained the lights together so only one switch is required. I do not think the previous owners knew how to add extra recessed lights to the chain and instead installed a new light fitting and switch.

It is as i said feed from a JB into the light fitting and then a switch off it. How this downstairs light interacts with upstairs is beyond me and all other light fittings in house work fine.
SquirrelHammer
Newly registered Member
Posts: 66
Joined: Mon Dec 04, 2017 9:59 pm
Has thanked: 4 times
Been thanked: 0

Re: Light switch only works when one is on.

Post by SquirrelHammer »

someone-else wrote:has it always been like this or what has been done recently?
It has always been wired like this apart from (me fixing the recessed light chain upstairs which i posted before).

The ONLY thing i have added is a fibaro dimmer module to the hallway (which works perfectly fine). but excluding this module, i do not see how this light switch connects to the light fitting or switch upstairs. This makes disconnecting or rewiring it that extra hard work
Ktuludays
Senior Member
Posts: 867
Joined: Mon Oct 27, 2008 11:23 am
Location: Dronfield
Has thanked: 233 times
Been thanked: 200 times

Re: Light switch only works when one is on.

Post by Ktuludays »

So if you can't fathom it and you've seen it how are we supposed to work it out blind? [emoji23]

Sent from my HUAWEI VNS-L31 using Tapatalk
If the lessons of history teach us anything it is that nobody learns the lessons that history teaches us.
SquirrelHammer
Newly registered Member
Posts: 66
Joined: Mon Dec 04, 2017 9:59 pm
Has thanked: 4 times
Been thanked: 0

Re: Light switch only works when one is on.

Post by SquirrelHammer »

Ktuludays wrote:So if you can't fathom it and you've seen it how are we supposed to work it out blind? [emoji23]

Sent from my HUAWEI VNS-L31 using Tapatalk
I was hoping that someone had some ideas of weird wiring they have come across that might explain this voodoo.

What are the chances of COM, L2 being wrong way around that might cause this?
User avatar
Dave54
Senior Member
Posts: 4504
Joined: Wed Feb 25, 2015 7:20 pm
Has thanked: 1128 times
Been thanked: 1037 times

Re: Light switch only works when one is on.

Post by Dave54 »

SquirrelHammer wrote:
someone-else wrote:has it always been like this or what has been done recently?
It has always been wired like this apart from (me fixing the recessed light chain upstairs which i posted before).

The ONLY thing i have added is a fibaro dimmer module to the hallway (which works perfectly fine). but excluding this module, i do not see how this light switch connects to the light fitting or switch upstairs. This makes disconnecting or rewiring it that extra hard work
So to put the question another way, did the 2 way switching work properly before your modifications, or has it always been faulty?
SquirrelHammer
Newly registered Member
Posts: 66
Joined: Mon Dec 04, 2017 9:59 pm
Has thanked: 4 times
Been thanked: 0

Re: Light switch only works when one is on.

Post by SquirrelHammer »

yes it worked fine before. I also don't see how taking a switch and recess light of can break it. if I remove upstairs switch the downstairs switch can happily turn lights off and on. no idea how it even connects to the light fitting
User avatar
Dave54
Senior Member
Posts: 4504
Joined: Wed Feb 25, 2015 7:20 pm
Has thanked: 1128 times
Been thanked: 1037 times

Re: Light switch only works when one is on.

Post by Dave54 »

SquirrelHammer wrote:yes it worked fine before. I also don't see how taking a switch and recess light of can break it. if I remove upstairs switch the downstairs switch can happily turn lights off and on. no idea how it even connects to the light fitting
This may be stating the obvious, but something you've done has broken it. There's no real "standard" way to wire these things, and one wire looks like another. Label the wires before removing them.
As for how to fix it, it's not easy to do from a description, but start where you made the modifications.
User avatar
someone-else
Senior Member
Posts: 10309
Joined: Sat Sep 01, 2012 6:03 pm
Has thanked: 24 times
Been thanked: 1757 times

Re: Light switch only works when one is on.

Post by someone-else »

SquirrelHammer wrote:yes it worked fine before.
Before what?
Fret not, a forum is a collection of opinions. Above, are mine.


Working on anything electrical? have you got a multi meter? why not? Would you hit a nail with a shoe?

If gloom had a voice, it would be me. :mrgreen:

:idea1: How to post a picture on this forum Click here

Video of how to resize / rotate pictures can be found on This page
SquirrelHammer
Newly registered Member
Posts: 66
Joined: Mon Dec 04, 2017 9:59 pm
Has thanked: 4 times
Been thanked: 0

Re: Light switch only works when one is on.

Post by SquirrelHammer »

well I reset it all back and no idea how this downstairs light links up to the landing so going to wait for wife and baby to go out and channel out the wall. gives me a chance to add extra switch and lights too.

I will just have to stick a wago or something on the end of the wires behind the switch as no idea where these are coming from. I know disconnecting them makes no difference to any lights.

I will prob end up rewiring the downstairs at this rate as I hate it how sparkys save wire by taking power from light switch rather than a jb.
User avatar
someone-else
Senior Member
Posts: 10309
Joined: Sat Sep 01, 2012 6:03 pm
Has thanked: 24 times
Been thanked: 1757 times

Re: Light switch only works when one is on.

Post by someone-else »

The norm is NOT to take power from a light switch since most light switches are just live and switched live.
To use JB's is not good either since apart from the fact they must be accessible they are another "joint waiting to fail"
The idea is there are as few joints as possible.
Fret not, a forum is a collection of opinions. Above, are mine.


Working on anything electrical? have you got a multi meter? why not? Would you hit a nail with a shoe?

If gloom had a voice, it would be me. :mrgreen:

:idea1: How to post a picture on this forum Click here

Video of how to resize / rotate pictures can be found on This page
SquirrelHammer
Newly registered Member
Posts: 66
Joined: Mon Dec 04, 2017 9:59 pm
Has thanked: 4 times
Been thanked: 0

Re: Light switch only works when one is on.

Post by SquirrelHammer »

someone-else wrote:The norm is NOT to take power from a light switch since most light switches are just live and switched live.
To use JB's is not good either since apart from the fact they must be accessible they are another "joint waiting to fail"
The idea is there are as few joints as possible.
Upstairs is fine I replaced all the ceiling roses with JB attached to joists, I can easily take a feed from upstairs to down as I am wiring a second switch from the landing. The downstairs is a mess, feeds are taken from light switches and there is a borrowed neutral from upstairs lighting so potential for feedback. Since I will be working on downstairs light switch for landing I might as well look at the hallway. I could easily take a feed from upstairs and JB it off but since I am looking at hallway I can hopefully figure it out and put a jb in. I need to do some tests on the wires and tracing as I need to make sure that the borrowed neutral lights are on the same breaker.
While doing so i might end up removing the wago connectors as i will know where the feed is coming from

The biggest issue is the mess from wall chasing and doing it when the wife is in a good mood

I replaced my ceiling rose upstairs with jb attached to joists in accessible locations. If this is not a good idea what other options are there? The idea was that i could then installer nicer light fittings than a pendant and i removed all the choc blocks wrapped in tape or covered in expanding foam.
Post Reply

Return to “Lighting”