Mystery lighting ciruit

8 Mar 2006
Reaction score
United Kingdom
Hi there,

I'm thinking of attacking this mystery I've inherited one more time before I get a sparky in. I have a 3 way switch in the hall, a security light on the wall outside, and a two way switch on the landing.

Downstairs switch
Downstairs connections
Upstairs switch
Upstairs connections

The first switch in the hall doesn't seem to do anything, and the security lights are light/motion activated, as if they are permanently switched on. the first switch doesn't affect them coming on at night it it's off.

The second two switches seem to have random effects.

If all switches are off the hall light is on.

With landing switches off and hall switches off (hall light on):
If hall switch 2 is on, both up and downstairs lights are on.
If hall switch 3 in on both lights are off
If hall switch 2 and 3 is on hall light is off, landing light remains on

With landing switches on and hall switches off (hall light on):
If hall switch 2 is on no change hall light remains on landing light off
If hall switch 3 in on hall light is off landing light remains off
If hall switch 2 and 3 is on hall light off landing light remains off

There are probably loads more combinations, but does anyone have any idea about what might be happening? Is it something to do with the switched live? All other lights in the house work fine.

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Needs more description.

what do the 2 switches upstairs do ?

need a better pic of the rear of the chrome switch.
I'm thinking of attacking this mystery I've inherited one more time before I get a sparky in.
The only sensible, responsible way to do this yourself is on the basis of a genuine understanding of how lighting circuits and switching arrangements work.

Electrical installation by trial-and-error guesswork is a very bad idea. There simply is no substitute for actually understanding what you are doing, and how the things you want to fiddle with actually work.

You need a multimeter, or a proper 2-pole voltage indicator and a continuity tester, not a neon screwdriver or magic glowing wand. And you do need to know how to use it, which means you do need to know how lighting circuits work so that you know what you are testing for where.

There really is only Plan A or Plan B:

  • Learn how lighting circuits are wired. //
  • Get a multimeter and learn how to use it.
  • Identify which conductors are which at the switches and the light positions.
  • Check for voltage present, circuit continuity, switches working etc.
  • Connect everything up properly.
  • Get an electrician.

Start trying different things without really knowing what's going on, hoping to get it working by luck, or by blindly following instructions to put-this-wire-in-that-hole without any idea as to why is not a plan.
I am suitably scared off. Now to find someone who will want to do this for less than a day's work.
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Sorry can't see enough with bottom switch to work out what is there.

Two switch better you can see reds on common and the closer one of the two the switch pair correctly wired.

Since at top switch red is common then also at bottom switch the common will be red.

But to work on the switch it's easy enough to separate out the wires in each cable and connect to each individual switch but from the pictures near impossible to work out.

So to start with you have look at the diagram
and decide which wires are which. But in the main it is the grey wire which goes to the common terminal which is important. The wires shown as blue and brown if swapped only means the switch works wrong way around.

Here is a better picture.

L - Blue with red sleeve
L1 - Yellow with red sleeve
L2 - Red
L - Blue

L1 - Yellow
L2 - Yellow
L - Red
L1 - Blue with red sleeve
L2 - Red

I'll look at the diagram - many thanks.
At first glance it would appear that the wires have been connected at random.

On one switch, there are two yellows,
the next has two reds
and the third, two blues.



You at least have to have the colours so that each three wires to each switch comes from the same cable.
The wires in your downstairs switch seem to be mixed up. Can you identify what cores come from what cable? You should have three cables coming in each with a red, blue and yellow.

The upstairs switch looks like it might be sensible enough - does it have two cables each with R,Y,B, and one cable with red and black?

Can you get into the outside light hall light, and landing light to check the connections there? Post photos if you can get into them.
No sarcasm intended - It's not my work and I will get a professional in if I need to.

Downstairs has three cores - each with red blue yellow.

I can't see the cores in the landing, and the cabling for the outside lights are difficult to access.

Hall ceiling rose
Landing ceiling rose
On the ceiling rose with the clear base, there is a blue wire just visible. Is it actually connected to anything or is it just tucked up in the back of the ceiling rose?

Make sure you have the electricity switched off to ALL your lighting circuits before you start poking around in there as the roses are always live even when they are not lit.
Looks like the left terminals of your first ceiling rose have had a serious overheating problem, possibly due to a loose wire. If so this rose will require replacement and any defective wiring cut back to achieve sound insulation
Don't think there is any overheating on closer inspection. Think it was just the photo. The main switch and all the breakers are off before I do anything.

This is what I found when I took the ceiling rose down in the hall. The blue wire was tucked in the ceiling.


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