Note the readings.
Then operate the switch, and repeat.
One of the readings should have changed from "open circuit" to a very low resistance (or vice versa if the switch was already on). Meters have different ways of showing open circuit, but you can see what it does when connected to nothing at all as per the above.
It sounds like you may have a LIGHTING RING CIRCUIT as opposed to a radial circuit.Hi Team
I have a very similar problem when i went to swap my main living room ceiling light. In total i had 3 wires. In each of those main wires i had 3 wires coming out red, black and green.
I had a spare bulb and wire connection so that i could check which one was live and which one was switch. What i found out is I had 2 live wires where the bulb came on.
Meaning i first connected the red and black from the main wire, the bulb came on. After that i connected the red and black from the second main wire and bulb came on. Later i connected the red and black wire on the last main wire and the bulb never came on, which means this is switch.
My only question now is why do we have 2 live wires in the rose ceiling outlet of a 1930 house ?
It sounds like you may have a LIGHTING RING CIRCUIT as opposed to a radial circuit.
One regular poster is likely to come on here and say they don't exist.
rather that such a ring is entirely unnecessary
I'll agree they are generally not necessary but I've worked on enough to know they are not 'that rare'. The other thing of course is how many people actually test for and identify a ring? I know that I for one will ensure I can identify the switch cable, isolate and change a fitting without ever testing to see which of the loop cables is in or out. For that reason I reckon that 90% of the ceiling light fittings I've worked on could very possibly be unidentified rings and I imagine the same is true for many others on here.Well, I will not say they do not exist, rather that such a ring is entirely unnecessary and more likely to be an accidentally created ring by who ever wired it, or a later error.