Intermediate switch tripping out

[hamerr]

I've taken out an external light - not sure if it ever worked - but it had three wires (red, black, earth) going to it from a kitchen light switch. (I'm assuming that when the kitchen light was turned on the outside light used to come on as well.) The three wires have been snipped short and now the kitchen light doesn't work. I've fitted an intermediate switch because there's now two red cables and two black plus earth. Depending on how it's wired I can have the light permanently on, or off, or its trips out. Other than tracing the wires back up the wall has anyone got an idea of what's going on?

 

[JohnD]

yes, you have done something wrong.

you mention the red, black and earth wire. You don't say where they are connected, what you did with them or what else you touched.

I'm guessing you did something at the ceiling rose, and didn't mark every wire and draw a diagram before you did it.

 

[hamerr]

Apart from earth, there's four wires coming down the wall; two red, two black. Originally two went to the existing light switch, two to the external light. When the external light was disconnected - by a joiner, so don't know if he did cock anything up - that's when the internal lights stopped working properly. Haven't touched the ceiling rose, just snipped the external light cables which I intended to cap off and have them hidden within the light switch. Now I have two red and two black wires, feeding into the intermediate switch. Before

 

[JohnD]

go up to the high street or DIY shed and invest £10 in a multimeter and we will explain how to identify the wires.

you will also need some red sleeving or tape, and some white vinyl tape, and a fine-tip permanent marker.

also a pice of plastic choc-block connector strip to park the wires in while testing. 5Amp grade will be fine.

If you have any bare copper wires, buy some green and yellow sheathing to.

 

[Space cat]

Let's clarify this a bit, bearing in mind that you can see the wires and we can't. When you say

Originally two went to the existing light switch, two to the external light.

do you mean that only two of the four (non-earth) wires went to switch terminals? How do you know that the other two went to the external light? Did they go out through the wall behind the switch?

Next question. Did you remove any wires from the switch while you were doing all this and, if you did, are you sure you put the right ones back where they came from?

I've fitted an intermediate switch because there's now two red cables and two black plus earth.

If there wasn't an intermediate switch there before, why do you want one now? Intermediate switches are only needed for three (or more) way switching. The good news is that an intermediate switch CAN be used as a single switch - and also as a two-way - IF you use the correct terminals. So don't bin it yet!

 

[hamerr]

Discounting earth cables; four cables came/come down the wall – hidden in plaster – and two went straight out through the wall to the external light, the other two went to a light switch. When a joiner disconnected the external light it was then that the kitchen lights went out until he capped them off. I think this is right as it was a couple of years back.

Since then I’ve had the external cables taped to the wall out of the way. All I did the other week was cut them down so that I could hide them behind the existing switch, and plaster over the hole in the wall

I fitted an intermediate switch on advice from an electrical wholesaler as I’d previously tried to put all the wires into the existing switch, but I’m still having the problem of either the lights are never on, always on or tripping the fuse.

 

[Spark123]

Can you post a marked up pic? It sounds to me like there may be a neutral in the switch - have you removed the cable to the outside light completely?

 

[hamerr]

Outside light has long gone, it never worked but that could have been due to the bulb. It was an ugly thing and went when I got a new back door and frame fitted. The cables to the external were separate from the internal, though running side by side for a bit. n earth cable for the external had been joined to the one for the internal. Other than that nothing out iof the ordinary. I'll take a pic of it al tonight and post it later.

 

[JohnD]

don't forget to buy the meter and other bits on the way home

 

[hamerr]

Hope this helps.

Untitled

• hamerr
• 16 Apr 2008
• 2

 

[RF Lighting]

They do look suspiciously like neutrals to me

 

[JohnD]

you decided not to buy a meter then

I can see four grey-sheathed cables. Does each of these contain one coloured core and one bare earth wire?

I can see that two of them are red, what colour are the other cores?

 

[hamerr]

Borrowing a meter at the weekend .

Two sheaths contain earth and red, the other two are black/dark blue. One each of the coloured cables used to go straight to the outside light, and an earth was spliced to the existing one/s.

I thought that by cutting the three cables to the outside down it would be okay, but obviously not and that's the big mystery. I've now fitted an intermeidate so that all the wires have somewhere to go - which makes me sounds simple!

 

[Space cat]

I've now fitted an intermeidate so that all the wires have somewhere to go

Sorry; couldn't resist that. You shouldn't have listened to a wholesaler whose first priority was to sell you a switch!

So, you once had one red and one black wire going to the outside light. One of those would be a neutral; probably the black one but, from what we know of the old wiring so far, nothing would surprize me! The other one should have been switched live for the light - but switched from where? Did that old light ever have a switch?

The remaining two wires (one red, one blacK) were, hopefully, the live feed and switched live for your kitchen light. We know you've got live power available in there, as well as a connection to your light, because you've had the thing lit. Your problem is therefore a fairly simple one (compared to some of the multi-switch corkers that come up on here): How do you identify two wires out of four?

You could just work your way through all six possible combinations but I don't recommend that because at least one of them will trip your breaker. A meter will help but you have to know how to interpret the readings. When you have multiple wires in close proximity, capacitive coupling can throw up all sorts of misleading results. My solution would be to use a light bulb - in a holder of course!

Select each of the six possible pairs of wires in turn and connect them across the bulb. Isolate the other two in choc-block. Now observe carefully what happens when you put power on. If the test bulb lights up bright, you have a live feed and a neutral. Now connect one of them (the red one?) and one other wire (a black one?) to the test bulb and try again. What you are looking for is a partially lit bulb and, at the same time, a partially lit kitchen light. Those are the two wires that you connect to the switch. DO NOT connect any other wires to the switch.

PS: If you want to use your nice new intermediate switch, use only two of its four terminals: one from each end.

PPS: If the old outside light never had a switch, you might find not one but two live feeds in there; so which one do you use? If they are both fed from the same breaker it doesn't matter too much but if they aren't ---

 

[hamerr]

That's me busy over the weekend then!!

Not sure where the switch was for the outside light, I kind of assumed it worked off the kitchen one. I guess it could have been taken out at some point, but the problem is that whoever has had the house previously didn't believe in doing a good job on anything, whereas I'm a pedant!