Light switch wiring


Hi folks,
Moved into this house a few months ago. In the loft is a (clearly DIY-job) light, with a light switch next to the entrance. It was temperamental at best, often requiring the face of the switch box to be jiggled up and down before coming on. Now it's completely packed up. In a testosterone-driven moment I removed the switch box face to take a peek, and one of the wires wasn't fixed in and was sticking out.
The problem is, I've no idea which circuit this switch is on, and don't really want to touch live wires (especially while standing on a metal ladder...). I don't know anywhere near as much as I'd like to about electricity and home DIY - is there a way to find out if there's a current even reaching the wires? I could buy a multimeter, but I still wouldn't want to touch anything so couldn't really fix it up. Should I just turn off all the electricity in the house and wire it back up? I'd have thought turning off all the electrics could damage some components, or something.
Also, the switch box has been over-tightened at some point I'm guessing, there're cracks emanating from the screw-holes. Is this a risk?
Cheers!
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Usually the loft light will be fed from the first floor lighting circuit, try having a look where the wiring goes from the switch and the light. Cracks from the screw -holes no problem, although the box may split at some point in time.
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Hi As stated it may be fed from the upstairs lights . Look inside the switch box .How many wires? what colour? If 2 red 2 black or 2 brown 2 blue with coper earth wires then the 2 blacks (blues) should be joined together with a connector block or even go right through. The remaining 2 reds (browns) go 1 in each side of the switch (or if it has 3 terminals 1 in com and 1 in either L1 or L2) Highly recommend you turn off ALL the mains before starting and use a good torch. Nothing should be interupted unless you have your PC on and the worst case is you will have to reprogram your vcr clock.
If as you say 'lectrics aint your thing always safer to ask a qualified sparks to give it the once over. HTH CJ
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Cheers for the responses everyone, very much appreciated. I think I'll get a new switch box face, turn off all the electrics, and give it a shot sometime soon. If I do turn off all the electricity at the main fuse box, I'm assuming I can freely touch the ends of the wires in the loft without anything happening? There won't be any built up charge or something?
Thanks again, you've all been helpful.
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naaah wont be a charge built up, well maybe a tiny one enough to light one of those led voltage tester screwdrivers for a few milliseconds,
but before i grab any bare wire i check it's deffo dead, wilko's sell a screwdriver tester for about 99p, not the standard ones with a neon bulb in them, they do one that has a couple of batteries in it and an led, it's sold as a continuity tester, microwave leakage tester etc,
you just need to put it near a live wire and it'll light up,
my self i'd have pushed the wire back in the terminal with a screwdriver or insulated pliers, and screwed it down when i saw it was out, but i know not everyone is happy to play with mains electricity like that, sure i'd have been stood on an alli ladder, but wearing rubber soled boots, and hopefully the ladder isnt earthed anyway.
Anyhow, if you get an electrical tester screwdriver, turn the circuit you think feeds the switch off, then check for power, if it's all dead, go ahead and put the new switch in, if you cant find the circuit breaker feeding it, even after trying the socket breakers, worry a little, but try the lecky shower breaker, house we had once the loft lights were wired to the nearest wiring junction on the celing behind, which happened to feed the shower's isolator switch,
and another house we couldent turn power off to the loft conversion lights and sockets at all, tracing the wires the last owner had put in took us through a small access hatch into the neigbours loft, where our loft electrics were connected to their lighting circuit in their loft!!!
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Cheers for that - I'll take a look in my local DIY shop for a continuity tester before I do anything. Hopefully mine's wired up through the neighbour's loft, I've been looking for a cheap way to run a media server - no electricity cost at all would certainly be nice!
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There will be a voltage of 230 volts at the switch even if the light is not on. If you touch the wire there will then be a current. Either buy something like this <http://www.screwfix.com/prods/56462/Hand-Tools/Detection-Equipment/Kewstick-One-Voltage-Indication-Stick to check for live cables of

Turning all the electricity off is actually a good idea. Just turn off your computers etc first, but even if you don't, nothing will blow if you just turn the electric off.

So treat yourself to a new switch when you do the work. Probably a quid at a diy store.
Adam
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