DIY Doctor UK DIY Forums

i m installing ceiling light the light works when the switch is off but when i turn the switch on it trips the main trip switch

hi, you have put all lives together & all neutrals together, right?
WRONG! see DOC's project section for wiring a light.
If old wiring is red/blk, then one of the blks would have been on its own in to Live of light as returning sw. live, other blks would have connected to Neutral of light , reds did not connect to light at all & would have been in seperate connector block looping to each other only
By putting sw-L. in with N when turning sw on will Cause a 'short-circuit' & trip MCB.

ched2be,
You have connected all like wires together. This will allow the light to work with the switch off but when you swith on at the wall you are causing a short circuit thus tripping mcb. Switch off mcb for light circuit and ID the switch wires. Depending on age of wires you will have red/browns(L) and black/blues(N) at the fitting. You need to ID the switch wires. The black /blue switch wire return needs to be sleeved brown. All the Brown/reds need to be connected together with a 10A block including the switch brown/red. The blue/black switch return wire (sleeved brown) will go into the light live. All the blues/blacks need to be connected together in a block with a blue wire connecting the block to the light N. I assume the fan light is metal so ensure all earths are sleeved green and yellow and terminated in the LIGHT earth block. Good luck with the arm ache.