Light Switch Wiring Query

[paulm]

In my workshop there is a double light switch, one side works the workshop lights and the other side switches power to an outside security light.

The security light doesn't seem to be getting any power when tested with one of the light up power detector pens, but the inside lights work and the cables in and out of the switch only light the pen up when the inside lights are on.

I think this means the switch is wired up wrong but not certain ?

On the right of the picture is the side that works the workshop lights and the left as you look at the picture is the security light side.

I'm also perplexed that the cable on the left has no neutral wire connected and has been snipped off which seems odd to me !

I remember replacing the security light a couple of years ago and I'm sure it was working at that time, so maybe the switch wiring is okay and the security light has just blown (I've changed the bulb and that hasn't helped) ?

Would have assumed it's the light itself except I'm just a bit puzzled that there seems to be no live indication at any time with any of the switch combinations which is throwing me a bit :?

I did have the soffits and fascias replaced recently on the outside of the workshop so I guess it's possible the wiring to the light has been disturbed as it runs in that space.

As a process of elimination it would be great if someone knowledgable on these things could confirm if the switch wiring is correct at least, in which case I guess I'll try a new light fitting next ?

Cheers, Paul

 

[woodstainwilly]

There is a wire missing from the lower cable (black)
No light can work with just one wire..
Willy.

 

[Chrispy]

Hi Paul I'm no sparky but your photo does make sence the red wire of the pair is the feed, the black is the switched live to the ws and the other red is the switched live to outside, all the neutral wires should be found in the light fittings the lives coming in and out also.
does your test work with the workshop lights turned on?

All the best

 

[Chrispy]

Me again, as I said I'm no sparky may be the lives are in the light fittings and the wires in the switch are all neutrals ie. neutral feed, switched neutrals the security light may need a permanent live. your test would only work when the light was turned on. (I think)

 

[Oryxdesign]

They've bridged the live from the workshop lights and taken a neutral from somewhere else directly to the light. Not unusual practise

 

[Eric The Viking]

The short of it is that we don't have enough info to give you a safe answer.

In your picture, IF, as I suspect, the red wire coming from the top-left is the incoming live, then the bottom left one is the live to the security system. The black wire is indeed the switched live to the lights (really should have red tape on it at the ends!). There are no neutrals shown in the picture, nor do there need to be, although I'd expect the earths from the twin+earth to be connected, in case the cable is severed accidentally (should blow the fuse).

There may be a problem with the neutral connection elsewhere, or the switch, or the connections may be faulty.

A neon pen _should_ detect live without the presence of neutral (it lights between live and earth, through you!), so, if your test is correct, it looks like at least a break in the live to the security light or a faulty switch or connection. Seen any rodents around recently?

Even that isn't the whole story though - as already mentioned, security lights usually have a permanent live and a switched one. That has to come from somewhere, and you need 3-core+earth to the fitting (live, switched live, neutral, earth). Fans with timers are the same.

If you have a spare, you could check the switch by substitution, but make sure the power is properly off first. I think you need a sparks though.

It's not that complicated really, but it's much safer to test with a meter than with those neon things.

Cheers,

E.

 

[paulm]

Me again, as I said I'm no sparky may be the lives are in the light fittings and the wires in the switch are all neutrals ie. neutral feed, switched neutrals the security light may need a permanent live. your test would only work when the light was turned on. (I think)

Hi Chris, that sounds sensible and matches what I think I'm seeing with the current tester ie nothing at the lamp, presumably as it's blown something inside.

I've just popped out to Screwfix and picked up a new better quality fitting that I'll see if I can fit in the morning before I go out for the day, otherwise it'll be next weekend.

Have you been sharpening everything in sight with the Tormek yet, it's addictive once you start, or maybe that was just me :lol:

They've bridged the live from the workshop lights and taken a neutral from somewhere else directly to the light. Not unusual practise

Thanks Simon. I wasn't thinking straight really, the light worked before so it must be the lamp, the switch wouldn't have changed by itself, d'oh (homer). Just threw me the way it was wired, nice to know it's standard !

Thanks guys, Paul

 

[Chrispy]

Yes I'm an addict and proud of it!

 

[paulm]

Hi Eric, I'll try substituting the light fitting as suggested, seems the most likely thing, and take it from there if not, probably swapping the switch out next and if all else fails running a new length of cable in case the fitters managed to put a nail through it or something while they were doing the fascias/soffits. A fair few rodents around too I suspect though !

Cheers, Paul

 

[Eric The Viking]

First things to check (when you can):

1. does the light have 2-core or 3-core (plus Earth) arriving? If only 2-core, and it has a movement detector, something's a bit odd.
It might have two twin+earth (one core not necessarily used), to achieve the same effect. It's not as neat, but I've seen it done as two-core used to be substantially cheaper.

2. You could substitute with an ordinary light bulb on a pendant fitting: get some "chocolate-block" strip to connect it (if there are two lives, use three terminals and try both lives in turn.

3. I meant, but didn't say, check the switch by substitution. They rarely fail outright without giving signs first - has it become hard to switch on/off? Again you can use your chocolate block to do this (switch on/off at the fuse box) - it's probably easiest.

All of the above do need switching off at the fuse box first, with one added complication:

If the security lamp has a movement detector, it should have a permanent live, and there is no sign of it in your photo. So, if there is one, then it's coming from SOMEWHERE ELSE. That's a cause for extra care, in case it might not be the same fuse/breaker! If you've done (1) above you'll know if there's an additional live. You can still test, but switch the box off properly first, before breaking/joining connections.

PIR switches themselves fail too. It may just be that.

E.

 

[paulm]

Thanks Eric, I'll try and work through it methodically in the morning. Appreciate the help.

Cheers, Paul

 

[Ateallthepies]

Just swap the two top wires first. This way you will see if the switch is broke as the inside lights will be on the other suspect side of the switch and wont work if it's broke.

Also to wire the switch correctly, the red link wire coming from the bottom right 'C' or common terminal should be taken out of the left hand side '2W' terminal and put into the top left 'C' terminal. Then move the red wire that goes to the outside light into the left '1W' terminal.

The common or C terminal is always for the permanent live whereas your 1W/2W are for the switched lives. As this is not being used as a two way switch like on your stairs lights, you only need use the 1W terminal, this also ensures the switch is in the proper 'off' position and not upside down.
Inside your switch there is a bar that is fixed to terminal C and connects with terminals 1W and 2W alternately each click of the switch just to let you know how they work.

Steve.

 

[paulm]

Just swap the two top wires first. This way you will see if the switch is broke as the inside lights will be on the other suspect side of the switch and wont work if it's broke.

Also to wire the switch correctly, the red link wire coming from the bottom right 'C' or common terminal should be taken out of the left hand side '2W' terminal and put into the top left 'C' terminal. Then move the red wire that goes to the outside light into the left '1W' terminal.

The common or C terminal is always for the permanent live whereas your 1W/2W are for the switched lives. As this is not being used as a two way switch like on your stairs lights, you only need use the 1W terminal, this also ensures the switch is in the proper 'off' position and not upside down.
Inside your switch there is a bar that is fixed to terminal C and connects with terminals 1W and 2W alternately each click of the switch just to let you know how they work.

Steve.

Good ideas Steve, and the switch does indeed seem to work upside down !

Cheers, Paul

 

[Boatfixer]

I have more than once managed to put a new halogen bulb in without locating the spring loaded connector properly into the bulb.... This causes much more up and down the ladders than strictly necessary!

 

[paulm]

I have more than once managed to put a new halogen bulb in without locating the spring loaded connector properly into the bulb.... This causes much more up and down the ladders than strictly necessary!

It's easily done isn't it :lol:

Didn't have time to have a look at it all this morning in the end due to a slightly lazy start to the day and going up to London to visit eldest daughter for lunch. Will have a go next weekend and hope to sort it out then.

Thanks to all for the ideas in the meantime.

Cheers, Paul

 

[paulm]

Put the new light fitting and pir up this morning, still didn't work

Next step was to replace the switch on the wall inside the workshop (in the pics in the original post), which was slightly confusing as the terminals in the new switch were arranged differently, but happy to say it then worked fine at the first attempt

None of the switch connections on the original seemed loose or dodgy so assume it must have been the switch itself, which I didn't think was the likeliest problem so didn't try that first before changing the light unit !

Thanks to all for the help and advice.

After lunch I'll try replacing the security light on the front of the house as well, as the pir doesn't seem to pick up any movement until you are quite close to it, so assume that the pir is failing on that one, fingers crossed that's straightforwards although there are two cables going into that one, but if I connect up like for like should be fine.

Then we're all sorted for the dark evenings

Cheers, Paul

 

[Eric The Viking]

PIRs can be damaged by strong UV light - or at least the plastic lenses can. I had one disintegrate, and the one we have facing south has become very insensitive.

If it's in strong sunlight, it might be worth organising some sort of sunshade for the actual detector.

May not be relevant though.

E.

 

[paulm]

Interesting, this one is facing south too Eric.

Has been there a few years though so I guess I don't really begrudge putting a new one up every now and again.

Cheers, Paul