Help please loft light only works with bathroom light on

[RDB73]

Hello there. I hope you can help me with this problem.
The loft light only turns on when I have the bathroom light switched on. I cut into the bathroom lighting cable (last in line) and connected into a 4 way junction box. (colour matching the wires, ie earth to earth and so on).
I then brought in the new cable from the new switch and connected into the same junction box, earth to the other earths, live to lives...the neutral (sheathing in brown) to the totally seperate terminal where i attached the live of the spur to the new loft light. The spur cable to the loft light then being wired earth to earths and neutral to other neutrals).
I think the cause of the problem is that the lighting cable i cut into from the bathroom ceiling rose runs to the bathroom light switch (switch lived side).
Its not too much of a problem more of a nuisance but is there a way I can remedy this so the I dont have to turn the bathroom light on to get the loft light switch to power the loft light?
Thanks :0)

 

[abrocky]

The cable with the brown sheath is not likely to be a neutral, it is probably a swiitched live for the bathroom.... Usea multimeter to confirm.

 

[Jase750]

Sounds like you've connected to the switched live instead of the permanent live in your jb. You need another jb for your new light then run the switch for it off that.

 

[RDB73]

You need another jb for your new light then run the switch for it off that.

Thats what I thought. How would I wire that up? I leave the original bathroom light cables wired as before, guessing wire the loft switch and light into another JB....then if I join the these two JB's toegther wouldnt I have the same problem, ie have to have the bathroom light switch turned on to allow the juice to go to the 2nd JB?

 

[TicklyT]

The cable with the brown sheath is not a neutral, it is swiitched live for the bathroom.

That would mean the both lights would stay on at half power until you operate one switch, which would affect the light you would expect to be controlled by the other switch.

OP - it sounds like you have intercepted the wrong cable.
Identify which wiring method has been used for your lighting circuit, then identify the 'loop' cables. These should have the permanent live and neutral you are looking for.

Switch drop cables usually have just a live and switched live.

Single cables to light fittings usually have just a switched live and neutral


your lighting wiring may be looped at the ceiling roses/ fittings (multiple cables in the fittings), or looped at the switches (multiple cables at the switches).

You may find a mixture of both methods in the same circuit.

 

[PrenticeBoyofDerry]

see below

 

[PrenticeBoyofDerry]

RDB73
Sounds like you know what you have done!
You have taken the feed to the loft from the the switch circuit of the bathroom light and not loop in of the lighting circuit.
What you need to do, is reconnect the conductors as they were originally.
Then find where the circuit loops in.
You will be looking for multiple sets of cable at ceiling roses, maybe loop in at switch plates or junction box connection within the loft.
It maybe that you do need some test equipment to help you ID the cables and the function they do.

Once you have found the loop in, you can the take live, neutrals and CPC(earth) to a switch the Neutral is not switched but terminated in to a connection block, and the permanent live is terminated at com of switch.
T&E then taken from switch to light. The blue core neutral terminated to connection block with the other blue core neutral and neutral of light, the brown switch live is then terminated at L1 of switch and taken to Live of light, all CPCs terminated at earth terminals.

Also remember if using the standard round junction boxes (white/black/brown) they need to be accessible for maintenance, inspection and testing, they cannot be put in an inaccessible location.

 

[RDB73]

Thanks tricky and prentice...I was just wondering...
Cos i've connected to the switch live of the bathroom, not the live, which is whats causing the grief,haha....is it safe just to run a seperate insulated live from the live side of the bathroom 2 way light switch (fan and light) to the live of the original JB, wiring into the jb live terminals. The actual bathroom light where feed would come from is correctly wired and earthed anyways,as is the JB and loft light switch... thus solving the problem of the jb connecting to switched live side ..sorry for being a nuisance. would this be safe to do.Thanks everyone. For info I used 1.5mm twin and earth cable on a 20amp 4 terminal JB,running a 36w florescent light.
Yep Prentice that's whats caused my problems,lack of free cabling in the loft so i could keep the junction box above the floor for maintenance.

 

[PrenticeBoyofDerry]

If the junction box is easily accessible for maintenance and I&T, it is okay.
Not sure why you would want to run perm live from bathroom switch (or are talking about fan isolator) to JB live.
You still have a functional bathroom light, what you need to do, is take a step backwards. Reconnect what you altered and do as I instructed.
I promise you, it's the most logical step.

 

[RDB73]

Thanks Prentice...was just thinking it might be easier. Cos I do'nt have any juice at the loft light even when switched on (cos it's fed from the switch live bathroom 2 way switch)...then I thought surely if I slotted an extra insulated live into the perm live connector of the bathroom switch itself, then this would take the perm live feed to the JB, and act as if the jb was wired to a perm live thus by passing the switch live connection). Was just thinking that would so the same and save me having to break into other cables and have more JB's in the loft. i think that would work in the same way, and was a clever workaround, was wondering if that was the case and if safe. I bow to your knowledge

 

[RDB73]

as before the bathroom switch and JB and loft swift all wired correctly and earth, so thought the new introduced feed may be a goer matey.

 

[PrenticeBoyofDerry]

It difficult to completely understand what you have, can you either do a diagram of current set up and then what you propose to do?
The problem is that you need two conductors to make the circuit, not just live but neutral also.
I recommend that you reconnect as previous and start again using the correct methods!

 

[ban-all-sheds]

You still have a functional bathroom light, what you need to do, is take a step backwards. Reconnect what you altered and do as I instructed.
I promise you, it's the most logical step.

 

[Greenie9657]

Hi JD
If you need to confirm the live you used mate, get out a multi meter across the live you used and the neutral. If there is 240(ish) volts there with the bathroom light off then you have a different problem. But with what you've already said I'm siding with everyone else and the only time you are going to have voltage there is when the bathroom light is on.

I've just re-wired my bathroom and when I laid all the cables in from previous light switch there were no lives there because all the lives were at the switch. Luckily I found this out before I had it plastered. It might be the same. If you only got 3 wires at the light fitting you must have the permanent live going into the sitch with hopefully is just as easy to get at in your loft.

 

[viewer]

To OP; you have the answer and solution, but here's a thought;

Could you accidentally leave the lights on in the loft? If so, leaving it wired through the bathroom might have advantages.