Switch Wire

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Morning all, this is my very first post. So here goes.
I have a bathroom light switch on the outside of a false wall. I have installed a couple of these 'soft touch' sensors which were suitable for leds. Now that we have little kiddies in the house to avoid disturbing them at night. Unfortunately, these units never seem to work, from memory I could never get them to turn off, I assumed that they may be dodgy units.

Luckily, I was on a construction site with some electricians, I sent them some pictures for advice. It appears i need a 'switch' wire' to make it work. There are only 2 wires going to the switch.

My question is as a complete novice how can i install this 3rd wire myself?
 
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If I understand you correctly, one of the two wires will be the switch-wire. One will be the live (always live), the other the switch-wire (only on when the switch is on).

Do the switches have just two terminals, or is there a third terminal marked N?
 
All of the soft-touch switches (all returned for a refund) from memory all have 3 terminals. I'm almost certain they had an N. Problem is I only had 2 wires :(
From memory when I turned the RCD unit back on, I couldn't turn the lights off. The dimming function kinda worked a little (i appreciate 4 led bulbs is maybe not enough for the switch to register the loading to work properly) but I could never get them to turn off.
 
If you have no neutral at the switch then no, they are never going to work. So you either need to re-cable so the loop in for the lighting circuit is at the switch instead of the ceiling rose or get some switches that don't require a neutral.
 
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All of the soft-touch switches (all returned for a refund) from memory all have 3 terminals. I'm almost certain they had an N. Problem is I only had 2 wires :(
From memory when I turned the RCD unit back on, I couldn't turn the lights off. The dimming function kinda worked a little (i appreciate 4 led bulbs is maybe not enough for the switch to register the loading to work properly) but I could never get them to turn off.

So your missing wire is the neutral, they will never work without the neutral, but I think you can maybe get version which do not need a neutral. There will be a neutral up by the ceiling rose or its equivalent in your setup.

These things need some power to work, when the switch is made/on, their power source disappears unless they have a neutral. Some get around that by having a rechargeable battery, others use a rechargeable capacitor as a power source when the light is on, recharging when off. They tend to have issues with certain types of lights, not recharging properly. A proper neutral is the best way to go.
 
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That's really interesting, thank you for the information. I knew I should have been a tradesman. I can setout bridges and roads but I know very little around the home :(

So it sounds like the easiest option is to be a light switch that doesn't require a neutral terminal although your comments about a rechargeable battery when completely over my head. How possible is it to install a new 3 core cable(?), tape it to the existing cable, and try and pull it out from the wall space leaving the new cable in place?
 
That's really interesting, thank you for the information. I knew I should have been a tradesman. I can setout bridges and roads but I know very little around the home :(

So it sounds like the easiest option is to be a light switch that doesn't require a neutral terminal although your comments about a rechargeable battery when completely over my head. How possible is it to install a new 3 core cable(?), tape it to the existing cable, and try and pull it out from the wall space leaving the new cable in place?

I'd say the chances of being able to pull a new cable through are very remote. By far the most usual method would be to channel back to the old cable remove and replace with a new one, suitably connected to the lighting circuit.
 
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How possible is it to install a new 3 core cable(?), tape it to the existing cable, and try and pull it out from the wall space leaving the new cable in place?

That depends upon the construction of the wall, if a stud wall it might work, if a plastered brick wall - no chance. You would have to make a chase to insert the extra cable and channel to protect it.
 
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It's a stud wall (the same wall for the shower pipes as well) then the loft above.
 
It's a stud wall (the same wall for the shower pipes as well) then the loft above.

Ok apologies, I was assuming it was a solid wall. If it's a stud wall then you may be able to draw a new cable down using the existing cable.
 
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It's a stud wall (the same wall for the shower pipes as well) then the loft above.

In with a reasonable chance then. You need to make a good firm connection to the end of your existing cable, with a strong draw wire, no bits stuck out to jam and pull it out the top whilst someone down below eases it in. You then attach your extra wire, or even better replace the whole thing with three a core from the ceiling rose, that will be Live, Neutral, Switch-wire and earth.
 
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I disagree that there is no chance of getting a new cable to a switch position in a solid wall.

If capping has been used, there is a good chance.
Sometimes you need to nibble a bit of plaster away right next to the box where the cable comes in, but this can often be covered by the switch.

But it depends on whether there is capping, and how many cables drop down.
 
You mention the lights appeared to stay on.
The switches may well have been correct and were 2 wire switches that did NOT need a 3rd Neutral wire.
The problem with 2 wire stuff is they use the wire to the lamps, through the bulbs , to complete the circuit to allow them to work.
Due to this Led lamps often tend to glow and appear to be on.
There are other ways to get round this and still use the 2 wires you have, you may NOT need to run extra cables
 

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