home wiring help - replacing light switch with 4 wires (2 red/2 black)

[wingers]

Hi
Hopefully someone can help me

Am replacing all the light switches in my house and have done them all without problem except this final one which is confusing me

The switch is a double switch but only one seems to do anything (kitchen fluorescent light), the other does nothing

It has 4 wires (2 red and 2 black), the 2 black go to two different common terminals and the 2 red go to two different L2 terminals

What type of switch is this and how do I replace it, as the new switches only have two terminals L1 and L2

This is the only switch for the kitchen light so it is not a 2 way switch or anything like that



photo attached which may help hopefully

Thanks in advance

 

[High Tower]

Is it just the picture or has it got a wooden back box?

 

[wingers]

Is it just the picture or has it got a wooden back box?

yes as answered previously in the post

 

[High Tower]

hmmmmm that will teach me to read the whole bloody thread in future!

 

[pushrod]

It sounds as if you have no earth (cpc) in your lighting circuits and the best remedy for this is to have that rewired. However it is not necessarily essential and just because your wiring is 40+ years old does not mean it is clapped out. Some of the old imperial cables can still be very good and have a lot of life in them. Your guy should carry out insulation resistance tests on the circuits and it is these results that say how good your cables are. Say you want an electrician friend who wasn't available to do the testing to look at them before you make any decisions and put them on here for people to look at.

Have a read of this re the lighting http://www.esc.org.uk/fileadmin/user_upload/documents/industry/best_practice/BPG1v2_web.pdf
if you have class 2 fittings (they are particularly well insulated or have no exposed metal parts) then it can be completely safe. Have a read of page 6/top of 7. If you have metal fittings ideally they should be replaced with class 2 but they can still be safe if they pass the tests on page 6 - addition of an rcd to the circuit if not already present can make it safer. Hopefully you will get a good guy who will explain all the options honestly and not someone who arrives on a horse!

 

[robsparky1975]

all depends on the amount of sockets you would want,downlights etc,surface wiring or recessed wiring,if you did want to go for a rewire then get a few quotes.

 

[pushrod]

thanks for all your replies

just had multimeter out and looking at the photo the left hand side pair which go to common and L2 show 0v when light on and 240v when light off, the right hand pair which go to the other common and L2 show around 80v?! when switch is on or off

?

In simple terms your voltmeter measures the diffence between 2 points.

When the switch is on both cables are live - there is no difference between them so your voltmeter reads zero.

When the switch is off one cable is no longer live - so the voltmeter shows the difference - which is approx 240V.

The usual way to use a volt meter is to put one probe on a known earth.

Think someone already mentioned the 80V could be an induced voltage.

 

[wingers]

today I turned power off, removed the switch and made sure all wires were not touching - then turned back on power and tested wires without the switch

one pair read 240v and the other pair still read 77v - so they must be connected to something, just not sure why 77v

will leave it to the electrician to investigate next week I think

 

[pushrod]

today I turned power off, removed the switch and made sure all wires were not touching - then turned back on power and tested wires without the switch

one pair read 240v and the other pair still read 77v - so they must be connected to something, just not sure why 77v

will leave it to the electrician to investigate next week I think

'tis quite possible they are just running beside live cables and that voltage is being made by a process called induction - very difficult to say without actually being there , but as you say the electrician should be able to tell for sure.

 

[cbw]

Rewire 2 bed bungalow 1750-2250

MK fittings throughout, downlights in kitchen etc.

 

[wingers]

spent a while in loft tracing the cables out of interest and one pair go to the fluorescent light and the other pair go to a junction box feeding other outlets, so it appears all four wires are to do with the light fitting - which means I still don't know how to wire replacement switch - so will leave it to the expert