2 lights, 2 switches, too few cables??

[RuthG]

I am trying to replace the old fashioned ceiling roses in my house with modern ones. The lighting circuit is a loop system and everything was very straight forward until the lounge.

I have a double switch and 2 lights, one for each switch, these work independetly (or did till I messed up). However there is only 1 cable comming from the back of the switch unit. The 1st ceiling rose has a feed from the loop, a switch connection and another (3 wire cable which was not originally connected and was actually taped up inside the old fitting). The 2nd rose has just one cable (presumably to the switch as it used to switch on and off independently of the other light).

I have replaced the 1st rose which works fine - although I have now connected the live and neutral wires which were originally taped up. BUT when I replace the 2nd rose - connecting as if I have only a switch cable, it is now permanently on.

What is going on? And how can I fix it?
Ruth

PS. Realise wiring was probably originally done by a muppet and am saving up to have the place rewired!

 

[billxiod]

You situation sounds like a previous DIY interference nightmare.

I know you won't want to hear this but you must get a qualified electrician in. Taped up wires, lack of earth continuity are recipes for distaster.

 

[Lectrician]

A more comprehensive description of what is the light with the 'loop' wires would help.

What type of cable leaves the light switch?? A 3 core and earth (red, yellow, blue)?? What connections are made at the switch??

 

[ban-all-sheds]

This is why, just like a screwdriver is essential for dealing with screws, and hammer is essential for dealing with nails, and so on, an essential tool when working on your electrics is a multimeter....

 

[RuthG]

Thanks for you responses, much appreciated. Here are some more details.

I have 2 ceiling lights in one room and one double switch which previously controled both lights independently.

In the switch I have 2 rows of 4 connections, 4 on top, 4 on the bottom, marked common-2way-common-2way, in that order.

On the top row a red wire connects the 1st 2way to the 2nd 2way and then exits the switch.

On the bottom row a blue wire is connected to the 1st 2way and a white wire to the 2nd 2way. Both then leave the switch. So the cable leaving the switch has a red, a blue and a white wire (very patriotic).

There are no connections to the commons.

The switch is connected directly to the first of the 2 ceiling roses, (which i foolishly installed to replace a connector and some tape). There are also 2 other cables - both red and black only. So in this rose i have 3 reds, 2 blacks a white and a blue.

The 2nd ceiling rose is not connected directly to the switch. The only wires in this 2nd rose are 1 red and 1 black which connect back to the 1st rose.

I realise I did bad in disconnecting the lot but it all looked so dodgy!
How can I fix it?

many thanks,
Ruth
ps. have bought a circuit tester - although now i look again its pretty obvious which wires are the switch.

 

[Lectrician]

I am sure if you look closer at the switch, you will have confused an L1 or L2 with the com.

But that doesn't make any odds, as you havn't altered the connection in the switch have you??

In the pendent, one of the two core cables will be the feed (a constantly live red, and a black neutral).

The other two core will be the loop to the next light, which requires switching.

The three core is your switch drop - one live down, two returning.

You need to identify which of the two core cables is the feed, and which is the loop to the next light. You will need a multimeter for this. I suggest you put a light bulb in the light with the single cable, and put your multimeter on ohms, and measure from L to N on each two core cable, looking for around 100ohm (give or take say 30 ohms depending on wattage). Once you think you have identified the correct one, remove the bulb, and check the resistance vanishes.

Then, once you are sure which cable is which, connect as follows:



The two blacks to the neutral of the new light (probably a blue core).

The red of the feed joined to the red of the switch cable with a connector block, seperate from everything else.

The blue from the switch cable to the live of the new light (probably a brown core). Identify the blue with some red tape or sleeve, to show it is really a live.

The yellow from the switch cable to the red of the cable to the looping light, again sleeve the yellow red, or tape it to identify it as a live core.

If the switch operates in reverse, interchage the yellow and blue at the switch or light fitting.


YELLOW = WHITE, sorry wrote the above assuming new-ish 3 core colours.

 

[RuthG]

Thanks Lectrician, it works like a dream,

you're a star!

Ruth

 

[securespark]

He only charges £60 ph......