Celing lights...

[englewood]

Hi there i have 3 black wires in my celing lights 2 are neutral and 1 is switch live how do i find out which 1 is switched live??

 

[Spark123]

It is the one which connects to the brown/red wire on the light fitting. This one should be marked with red sleeve to signify it is live.

 

[englewood]

hi there non of them are marked with a red sleeve.

 

[Spark123]

By this, can I assume you have taken the old light down?

 

[englewood]

hi there tried all 3 black wires 2 leave a constant feed and cnt turn off by switch and the other trips the fuse out.

 

[englewood]

yes i ihave taken the old light down

 

[andy]

yes i ihave taken the old light down

go get multimeter. turn power off. test resistance between red and black. when you flick the switch, 1 wire will go between high and low. this is your switch cable. and you should have marked the switch cable first

 

[Spark123]

You need a multimeter. Firstly switch the supply off. To find a switched live, separate out all 3 black wires. The three red wires should go together but nowhere else. With the mutlimeter set to ohms range, get somebody to operate the switch and measure between the red wires and each of the black wires in turn. The switched live is the one which shows low resistance when the switch is operated / high resistance when switch open.

 

[englewood]

non off my black wires are operating as a swicth wire, why is this?

 

[Spark123]

The switch could have blown if it has had a short CKT across it, what type of switch is it? Take the switch off and test across it with the mutlimeter to see if it is switching.

 

[englewood]

ok sorted cheers guys.

 

[andy]

non off my black wires are operating as a swicth wire, why is this?

if you have connected all blacks and all reds you could have blown the switch, as pointed out by spark123. in this case replace the switch. if this is not the problem, try finding the cable to the swicth by holding 1 lead on the black at the switch and test for a low resistance at a black at the ceiling. you might need a longer piece of cable to do this