Problem replacing a double on-way dimmer switch

[bigalm]

Hi,

I've just moved to a new (old) property and wanted to replace all the old brass sockets and switches.

In the lounge I had a double dimmer switch (rotate switch only) with each switch independently controlling two wall lights. I removed this and found the following connections:

blue - L1 on one side
yellow - L1 on other side
red - COM on one side, plus a short red loop to COM on the other side.

(no earth - which was a bit of a worry as it's a brass fitting!)

As the switch was a one-way fitting, L" was blanked off.

There was also a black wire that didn't appear to be connected to anything.

The new white plastic switch says it can be one-way or two-way, but I just connected it all together in the same way as the old one.

I switched on and it works fine except when I went into the dining room I found that the light wouldn't turn on there at all! There are five bulbs on a central pendant, so it wasn't just a bulb blown by coincidence.

The switch in the dining room is immediately behind the lounge switch.

I'm now thinking that the black wire wasn't disconnected but was just loose and came away as I removed the old switch from the housing. How do I safely check this, and would it just be a case of connecting it into one of the COM connections??

Any help/advice would be greatly appreciated.

 

[bigalm]

That should be L2, not L"

 

[ericmark]

There are all sorts of systems used to give lights the control desired. There is no rules saying black should be X. In new system just three colours brown line, blue neutral and green/yellow earth and with two way all line conductors be they switch on not then they should be sleeved brown.

Old system brown = red, blue = black but be it grey or yellow they should be over sleeved brown or red depending on age.

Switches can have a com or L1 or L which means when changing the switched outputs can be labelled L2 and L3 or L1 and L2 which does not make it easy.

I never worry about switch labels I always test the switch too easy to mix up a change over and intermediate switch.

 

[bigalm]

Thanks for your reply, but how do I (safely) determine what this 'spare' lead is and whether this is the source of the problem or if I've wired up the switch incorrectly? I realise the colours are largely meaningless at this stage, but that's all I have to work with and why I tried to simply wire up like-for-like.

 

[PrenticeBoyofDerry]

You need to inspect the com or permanent live of the switch that does not work in dinning room, see what colour core it is, if black then test continuity between that black and lounge black.
If you can confirm continuity between both ends, then chances are this is a link conductor between the perm lives of the lounge switch. This can then be terminated with coms of lounge switch.

 

[bigalm]

No. Original switch was a double gang (two switches on same plate) but each switch is one-way i.e. each switch independently controls two wall lights. You switch each pair on and dim them with just the one switch.

Each side has L1 L2 (blanked off, no screw) and C.

The new switch CAN be used as a two-way but I don't need that facility. It is labelled the same L1, L2, C with all connectors available. I just moved all like for like and this switch seems to work fine. It's the dimmer switch in the next room that doesn't work now. I've tried replacing this with a simple single one-way switch and it still doesn't work.

I'm thinking that the wire that seemed to be just hanging spare may be a loop back for the switch on the other side of the wall. Is this normal?? The light in the dining room seems to be the only one not working. Is it safe to connect it to one of the COM terminals to test this??

It's an old house and the colour coding is different in each box. The lounge is red, blue, yellow (plus this extra black one) whereas in the dining room its red, black plus green/yellow earth.

 

[bigalm]

Sorry PrenticeBoy, I seem to have replied to a comment of yours that's disappeared. Your advice is sound and seems to confirm my line of thinking. I'll work on it more in daylight tomorrow. Thanks.

 

[PrenticeBoyofDerry]

Do you have multimeter, if so I suggest that you test for continuity between the two blacks in each switch, this is a dead test, so isolate circuit.
Does the black core in lounge switch have bare conductor at the end as if as though could have been loose and come out, but there is nothing to say it has not broken in terminal.

 

[PrenticeBoyofDerry]

Sorry PrenticeBoy, I seem to have replied to a comment of yours that's disappeared. Your advice is sound and seems to confirm my line of thinking. I'll work on it more in daylight tomorrow. Thanks.

Yes I apologise, reread your post and then rewrote mine, as it was irrelevant to your issue.