Changing a ceiling rose which has 4 two core wires

[gsmoran7]

Took down two old hallway light 1 and light 2 ceiling roses to replace with two new light fittings. Both lights were working before, both lights are controlled by the same switch system(one downstairs one upstairs). So managed light 1, but got carried away and forgot to mark switch wires live from the old light 2 rose before removing!!!!!!

There are four two core wires each with red black earth, I'm calling these A,B,C,D.

Took ohm reading for each.
Wire A - Low resistance & no change when flicking lighting switch - What does this do connect lights or switches I'm thinking, this is wires to light 1 rose which should cross over (live to neutral, neutral to live) ???
Wire B - Low resistance then High resistance when flicking switch - This is the switch wire ??
Wire C - High Resistance - Loop wire in or out??
Wire D - High Resistance - Loop wire in or out??

To confuse me more, wiring on the light 1 has a black and red from two different wires of the four that are wired to the lights brown live connection, remainder three reds looped and three black to blue neutral connection on the light fitting. I think I remember this was how light 2 ceiling rose was wired but which wires!

Tried many different arrangements but can't get it wired up correctly. Best I can get it is wires B Black switched live to Brown light fitting B,C,D reds grouped to live loop then B,C,D blacks grouped together A red left isolated - so light 1 works and so do the rest of the looped downstairs lighting circuit, but obviously light 2 not. If I put A red into switched live then circuit shorts if switch turned on. How can i test what wire A is?

I have an analogue multi meter and a voltage screwdriver tester.

Please advice as it all worked before I tinkered and the circuit hasn't been altered!!

 

[Taylortwocities]

these resistance readings.

These are taken from where to where?
Are you measuring from red to black on each cable, or what?

When you say "low" and "high" resistance, would you like to qualify that?

Low resistance might be 0.02ohms
High resistance might be 10Megohm

 

[gsmoran7]

Sorry! Yes measuring from red to black on each cable. Low resistance was 0 ohms and high was around 10 Megohm

Many thanks

 

[bernardgreen]

To confuse me more, wiring on the light 1 has a black and red from two different wires

Most likely that black is the switched live coming from the switch (it should be sleeved red ) and the red is the switched live going to the other lamp.

That black should be in the cable that showed different resistance when the switch was operated. You can check which is the one to the other lamp by putting a filament lamp in a that will give a low ohms reading then remove the lamp and the reading should change to high resistance.

 

[Taylortwocities]

So is there a second light that also operates with your problem light.
How many cables/wires at that point?

 

[gsmoran7]

gsmoran7: To confuse me more, wiring on the light 1 has a black and red from two different wires
bernardgreen: Most likely that black is the switched live coming from the switch (it should be sleeved red ) and the red is the switched live going to the other lamp.

Hallway Light 1 rose I have replaced fitting and is working, so it is Light 2 rose which I can't work out what to do with all four wires.

So is there a second light that also operates with your problem light.
How many cables/wires at that point?

Yes there are two lights in the hallway Light 1 and Light 2 both have 4 two core wires. Light 1 has been replaced and works and has black and red from two different wires of the four that are wired to the lights brown live connection, remainder three reds looped and three black to blue neutral connection.

Thanks

 

[securespark]

So light 1 works even with the wires you have hanging out of the ceiling and disconnected??

 

[gsmoran7]

Yes Light 1 works and switches on and off when wire A is disconnected from wiring in Light 2 (obviously Light 2 doesn't work), and lights on the rest of the downstairs lighting circuit all function.