Simple wiring query for Dimmer Switch

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Hello,
Can someone please help...
I am tring to install a dimmer switch.
I have two lights in a room controlled by one switch.
The old switch was wired as follows:- L1: Yellow with red tag L2: Red L3: Blue with black tag
I have bought a dimmer switch with the connections labelled as follows:-
'Picture of a sine wave with an arrow through it' (lets call it SA), L1 and L2.
First attempt...:- SA: Blue with black tag L1: Yellow with red tag L2: Red and when I switch the circuit breaker on, it switched straight back off.
Second attempt...:- SA: Yellow with red tag L1: Blue with black tag L2: Red and when I switch the circuit breaker on, although the breaker stayed in place, the switch would not work.
Can someone tell me what should work.
Thanks in advance. Fred
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<snip loads>
</snip loads>
I apologise if this answer appears rude in any way, but I think you should leave well alone.
Don
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http://www.diydoctor.org.uk/projects/dimmer_switches.htm
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<<<snipped>>>
Are you sure that all connections were made in the old switch, and that they were as you say above? If yes, then the switch is a two configuration that has two switches, one either end of the room, which control the same lights. Is this the case? If so, then the switch you have will not work at all on this type of wiring configuration.
If you look down this page: http://www.diydoctor.org.uk/projects/lights_and_switches.htm you'll see the wiring scheme for a two way switching system like yours sound as though it is.
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BigWallop wrote: <<<snipped>>>

I am certain. No, there is no second switch. It's only a 2-year old property if that helps.
Fred.
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they
that
lights.
on
Did you take a look at the web pages on the link I sent? Did your switch wiring look like any of the wiring to the common layouts in the pictures?
For the switch to have three terminals all used, it is a two way switching scheme. A common single way switch plan, even in two and three gang switch layouts at the plate, is to have two terminals. The two terminals will be marked in either a COM to L1 or L1 to L2 plan inside them.
The switch and connection scheme you describe is for a two way switching layout, were two switches control one light fitting in the room. Two way switching simply works by swapping wires so that the second switch can pick up a live feed.
Please take a look at the wiring schemes on the http://www.diydoctor.org.uk/projects/lights_and_switches.htm and make note of how the different switching schemes work. Then you'll have a better idea of how to make your system work properly.
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Thanks for staying with me so far...
I took a look at the web page and the wiring shown on that page in the 2nd switch of the diagram labelled TWO- AND THREE-WAYSWITCHES, is very similar to the way it was before I touched anything, except: -
C = L1 (BTW I just noticed the word COM near the L1 wiring point) L1 = L3 L2 = L2
So the wiring points are arranged as
C L1 (COM)
L1 L2 L3 L2 diagram mine
The switch unit I am taking out is a Volex 1000 series 1 way switch.
I'm not suggesting that the wiring was done brilliantly but I am certain that there is one switch in the room controlling 2 lights and it works.
I had thought this would be a really simple query and I just wanted to avoid trying all the permutations of 3 wires and 3 holes. However, now I'm a bit confused!
Is my setup really strange? Did the builders/electrician use switch in an unusual way?
Either way, is it any clearer how to make the dimmer work?
Fred.
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Getting a one way dimmer to work on a two switching scheme isn't any clearer with the wiring plan you say you have at the switch. How does this switch control the two lights? Does it go up for one light and down for the other? Or is it just on and off when the switch is moved?
You have three wires where there should only be two, so this is why I think the system is wired for two way switching configuration. My next bit of advice is, start looking behind things, or in another room, for another switch somewhere that also controls these lights, because you've even got me stumped the way it is now.
Sorry mate, but need more info' on this.
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I've been away for a while but I'm still alive unlike my dimmer.
The switch switches both lights on and off simultaneously. No other switch controls these lights.
However...

Whoops, deep embarrassment here...
It's a 2-way .... I saw 1-way marked inside but it is marked next to the L2 point.
Sorry this was very dim of me :D
Fred.
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Hi BW
Long time since I spoke to you.
Heres a theory for you. If the switch is a 2 way switch then no matter how incorrectly the switch is wired the MCB should not trip. All 3 wires are tagged as live on such a circuit and it would not be possible to create a live/neutral short.
Now. On the old switch the blue was tagged with black which suggests neutral. If L1 is permanent live and L2 is neutral then the common terminal is switching between live and neutral but the two do not meet. The switch would work. Look again at how the OP first wired up the dimmer and you will see that he has fried it.
Only a theory
Adam
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<<<snipped>>>
If
switching
he
Hi Adam. How's you? Keeping busy I hope.
As for your theory on the wiring scheme. I thought the dimmer switch might have been fried from the start, but I didn't want to be the one to break the bad news to him. :-)
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Ok, lets assume I fried it.
I have a brand new one, still boxed.... Now, other than leave it in the box, can anyone suggest how I should proceed...
Thanks! Fred
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Are you still sure there is only one switch in the room controlling both lights? I have no reason to doubt you.
Adam
PS Have you got a multimeter that can read over 240 volts ac?
Adam
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Yes, Im still sure. One switch controlling 2 lights which go on and off at the same time.
To recap, the wiring on the original switch is:-
L1 (COM) <------- Yellow cable with Red tag O
L3 O O L2 <------- Red Cable ^ \\--------- Blue with Black tag
Presumably my second attempt is the most likely solution (only the first attempt fried things so it wasn't proven)?
Second attempt was ...:- SA: Yellow with red tag L1: Blue with black tag L2: Red
Unfortunately I dont have a multimeter but as a separate thread I would appreciate a recommendation, together with a pointer to a tutorial on how to use it in this sort of situation.
Fred
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Try using the original lightswitch with the blue wire terminated into a piece of strip connector instead of the switch and see if the light still works.
Adam
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And the rest of the message should have read.
If the light works when you have done this then use the yellow wire to SA and the red wire to L1 on the dimmer switch leaving the blue wire in the strip connector.
Adam
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It worked!!!!
Leaving the blue wire out of the original switch allowed that switch to work as before. Then wiring the dimmer as you suggested also worked.
Thank you!
Can you please explain why it worked and why the blue wire was wired as it was originally. Fred
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I assumed that the blue wire was connected to neutral as it was tagged with a black ring. The original set up only worked because the permanant live (your red cable) never came into contact with the blue cable. The switch was either connecting L1 to L2 or L1 toL3 but L2 and L3 never make contact. Your first attempt with the dimmer connected the live to the neutral and destroyed the dimmer. Your second attempt with the dimmer may still have failed even though it followed the original wiring diagram. As some lightswitchesdo not always make a clean break between the contacts as they are switched and you may momentarily get all 3 terminals touching each other inside the switch. The result would have been the same (ie destroyed dimmer)
The wiring as it was originally done was incorrect, so have a look around your house at the other one way switches and see if any others are wired up in the same way. If so then terminate any blue wires with a black tag with some strip connector. The main fail point would be that the yellow wire is marked as live using a red tag but it is obviously neutral when the light is switched off
Adam
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Thanks for staying with me so far...
I took a look at the web page and the wiring shown on that page in the 2nd switch of the diagram labelled TWO- AND THREE-WAYSWITCHES, is very similar to the way it was before I touched anything, except: -
C = L1 (BTW I just noticed the word COM near the L1 wiring point) L1 = L3 L2 = L2
So the wiring points are arranged as
C L1 (COM)
L1 L2 L3 L2 diagram mine
The switch unit I am taking out is a Volex 1000 series 1 way switch.
I'm not suggesting that the wiring was done brilliantly but I am certain that there is one switch in the room controlling 2 lights and it works.
I had thought this would be a really simple query and I just wanted to avoid trying all the permutations of 3 wires and 3 holes. However, now I'm a bit confused!
Is my setup really strange? Did the builders/electrician use switch in an unusual way?
Either way, is it any clearer how to make the dimmer work?
Fred.
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This may work.
The black ring is the clue. It is (or is identified as neutral by the presence of the black tag). Put the blue wire into a piece of strip connector and do not use it. Then put the red into L1 and the yellow wire into SA on the new switch.
You have probably destroyed the dimmer by now by discharging a large current through it's circuitry and so the above may not work. If so then to prove (it won't actually prove but it will go some way to showing that you have) only have a one way switching system then do the above using L1 and L2 on the original switch. ie Do not use the blue wire.
Adam
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