light problem

[ojo1]

I can carry out simple electrics, new lights, sockets etc. New kitchen and between it and the main house is an old utility room.At the house end we blocked an old door and unearthed a light switch for the room. I wanted this moved to the kitchen end of the room,so I thought simple ,disconnect switch,put cable into junction box and extend down the room. Switch is an old double switch, I opened it and found 3core and earth. 2 x commons joined by red wire, yellow wire into B 1way, cable red into Bcommon, cable blue was covered in yellow tape and in A 1way.
I terminated the yellow and used the red and blue to feed junction. Light worked fine but then I wanted to isolate light circuit for another job and it refused to turn off at the box. Not sure if wiring is a problem or possibly the old simplex cartridge in main box is faulty.Help

 

[PrenticeBoyofDerry]

could it be that that light, is not part of the circuit you are isolating?

I would remove fuses individually until that particular light goes off.
I would also double check that the light is not powered by two fuses.
Once you have determined that you can do a little investigation into where the power is feed from, could be a fused connection unit from a socket circuit.

 

[ojo1]

Thanks for fast response.at the time the light was actually on , i told my son to isolate ,he switched off at box but the switch went straight back on although light did go off then on at the same time. I switched off the light and the isolator could then be turned off. At first I thought I'd connected wrong wires in junction box so I disconnected and reconnected the original switch. We still had problems with main fuse which made me think this is a coincidence and we have a faulty switch in the box

 

[Aragorn84]

Take a photo of the part that "turned itself back on"?

Sounds very odd.

 

[PrenticeBoyofDerry]

what about other lights on the circuit, do they react the same way?
if you are opening a trip switch on a mcb and the switch is not opening the circuit, then it is very likely that is at fault. So how did you disconnect and reconnect this switch if you could not power down, did you isolate the whole system?

 

[ojo1]

This was the downstairs light circuit and the other lights acted ok. I did close down the mains so I could disconnect the switch, I thought I'd misunderstood the original wiring and connected the wrong ones to the junction box, It was still playing up after I'd reconnected as original.

 

[PrenticeBoyofDerry]

so all other downstairs lights are isolated when trip is opened, but this one not?
Have you tried any other circuit breakers to see if they isolate it?

 

[ojo1]

sorry didn't make myself clear. When my son tried to open the trip all the downstairs lights ,including this one went off but came straight back on as the trip refused to stay open. Then when I switched this light off at the wall switch and he opened the trip it stayed open and all the downstairs lights were isolated including this one. I'd started thinking I'd misunderstood the switch wiring and made a mistake but then I got to think that maybe it was a faulty trip

 

[PrenticeBoyofDerry]

sorry didn't make myself clear.

Still not too clear

When my son tried to open the trip all the downstairs lights ,including this one went off but came straight back on as the trip refused to stay open

Okay that sounds like the device is knackered

Then when I switched this light off at the wall switch and he opened the trip it stayed open and all the downstairs lights were isolated including this one.

Have you repeated this procedure, as it may have just been coincidental?

I'd started thinking I'd misunderstood the switch wiring and made a mistake but then I got to think that maybe it was a faulty trip

It could well be, what type of device is it? Sometimes the make/break contact mechanism packs up and will not allow you to isolate, but it may work intermittently but would still require replacing.
If you have a multi-meter or continuity tester, you could test the breaker to see if it is opening and closing.

 

[ojo1]

It's an old Simplex cartridge. When the new kitchen is finished we have an electrician who will install a new box etc, we just have to make do with this one till then
Is that light switch wiring something you've seen before,as I said I've never seen a neutral wrapped in yellow tape