2 way dimmer switch

[Rantallion]

I want to replace a 1 gang 2 way switch with a dimmer switch. The old wiring is 2 cables each with 1 red and 1 black wire plus earths. The red and black wires from one cable go into two holes marked L1. The other red and black wires from the second cable go into two holes marked L2. The new dimmer switch, which is a 2 way dimmer, has a C, L1 and L2 hole. I understand that one of the wires is the live which goes into the C. That leaves me with three other wires and 2 holes!

[John Rumm]

Its late, so try this as a quick answer:

if that does not help, then more information will no doubt follow later ;-)

[dennis]

Is there only two switches that operate the lights or are there three or more?

[ARW]

An intermediate switch:-) But it matters not as the OP is using DIYBanter.

[Rantallion]

Thanks for the link. Looks like my wiring is the old 'alternative' method of 2 way switching with 2 core plus earth not three core plus earth cables, probably with a borrowed neutral. Am still confused about how I can wire it to the new dimmer. Think I might have to give up or get a sparky unless you've got any other ideas.

[John Rumm]

Ok awake now...

still not making much more sense alas - a photo would help.

A normal single gang two way switch should have three terminals, C, L1 and L2 - i.e. exactly the same as your new dimmer.

A two way switch is a changeover switch - the C terminal is connected to either the L1 or the L2 terminal depending on the position.

Hence your comment about what sounds like multiple L1s and L2s does not seem right if we are talking about the same things....

Could you possibly have an intermediate switch?

This has 4 terminals rather than three?

How many switches have you in total that control the light?

How are the others wired?

[dennis]

There are dimmers that need a neutral so they would have 4 terminals but they would labelled wouldn't they?

[Dave Plowman (News)]

Domestic dimmers? Never seen one. And the first dimmer I ever saw was in the '60s. Still just replaced an ordinary light switch.

[ARW]

Go B&Q they sell them:-)

[ARW]

Considering that the only dimmer switch that the OP has is still in it's packaging then we can forget that comment.

[Rantallion]

There are 3 switches so I'm guessing its an intermediate switch. There's 2 switches on top of the landing and one down stairs. The top 2 are both wired the same way, haven't checked the downstairs one but I want the dimmer upstairs. Need to keep a light on for the kids at night but its too bright and drives me bonkers!

[John Rumm]

Its sounded like his existing non dimmer switch has 4 terminals...

[John Rumm]

ok that would makes sense. If you check one of the other two switches they ought to be the three terminal types. Replace either one of them with the dimmer and that will then do what you want.

[Rantallion]

Thanks.

Had a look but all the dimmers I could see in the shops had three terminals.

Think my switches are definitely intermediate switches. Don't know if its possible to replace one of these with a dimmer.

[John Rumm]

Yup, and that is all you are likely to find.

You have two options...

1) Ignore the intermediate switch and leave it alone, and replace one of the other switches (i.e. one of the proper three terminal two way switches), with a two way switch dimmer. That give you brightness control from the one switch position, and on/off control from that and the others.

2) Replace all the switches with one master dimmer, and a number of slave dimmers. You may need to wiring changes at the intermediate position. This will allow on/off and brightness control from all switch positions.

[dennis]

8<

3)

leave the wiring as it is and fit