new light fitting blowing breaker

[kyranocat]

hi guys hoping to get some advice, our porch light has been removed as the entire porch is being redone but the 2 cable feeds were not identified i have checked polarity on one and i am certain this is the switch wire leaving the second cable as a mains feed cable .The problem is every time i wire a light onto these cables the circuit breaker trips as soon as the light switch is clicked into the on position.I am lost on what the issue might be.Polarity has been confirmed on the switch wire so thats correct and the mains cable turns live then the breaker is in the on position aswell.I dont think its an overloaded circuit either as both lights are the same wattage and even tried wiring the old light back on to check (SAME SITUATION OCCURS).
I am hoping someone might be able to shed some light on the situation(no pun intended).Thanks

 

[TaffyDuck]

yes rcd is tripping[/QUOTE

fault current

If the switch is recessed into a metal box check that the set pins on the switch have not knicked the live inside the switch

 

[rich.250]

Rcd and or mcb?

 

[telectrix]

"cut the blue wire".

 

[TaffyDuck]

"cut the blue wire".

Hurt locker?

 

[telectrix]

richard harris in the film juggernaut. unexpolded bomb.

 

[ample current]

you are going to have to test the circuit then with an mft then to identify the fault.

 

[telectrix]

i'll lend out my neon screwdriver for a modest fee.

 

[TaffyDuck]

i'll lend out my neon screwdriver for a modest fee.

Nice one, I just use my finger, if it hurts its live

 

[kyranocat]

i was suspicious about if i had correctly identified the switch so on top of using a continuity/polarity indicator i have nicked a MFT from someone to test the continuity and it does confirm its the switch wire. got a reading and then flipped the switch to get an open circuit so i am going to try testing the circuit more indepth later in the week.I am wondering if i should try and replace the switch to see if its the issue, will post back later with an update.

 

[trev]

Nice one, I just use my finger, if it hurts its live

You big jessie
Get your tongue on it. It's the only way to test live/dead
YYYYYYYEEEEEEEEEEEEEEEEEHHHHHHAAAAAA

 

[ample current]

not sure if this would be considered good practice, but have you tried connecting the incomming live and neutral to the lamp connectors directly missing out the switch and switch wire altogether to see if that trips the breaker.

 

[Hawk81]

Is this your own porch or not? If its wired in new colours it not that old a wiring then. I take it all was ok before the light was removed?

 

[Knobhead]

I’m sorry but two cables doesn’t give a lot of options.
If you’ve borrowed a MFT do you know how to use it?
A competent electrician will find the fault within ¼ hour.
If building modifications have been done the chance is cable damage!