I fitted a new 2-way dimmer switch at t’foot of our stairs yesterday. It’s got two dials one it, one controls our living room which works fine, and the other the light at the top of our stairs on the landing.

When the dimmer is turned on we can turn it off at the dimmer, but not using the normal light switch at the top of the stairs. If it is off at the dimmer we can turn it on and off using the upstairs switch.

What’s going on? The switch is wired in line with the instructions (although, I note, not the same as the switch we removed) – Red to L1, Blue to L2, Yellow to the squiggly symbol.

Thanks.

not the same as the switch we removed

and did it work previously? There’s no guarantee the wiring was done to standard.

How is the other switch wired?

I always take a photo of stuff before I unwire it.

if its a like for like replacement, does it work if you wire it up like it was…

Sounds like you may have not wired it up as two way.

Sounds like you may have not wired it up as two way.

This. You’ve got two wires arse about face.

not the same as the switch we removed

… and that’s why. In domestic wiring the only thing wire colours tell you with any sort of reliability is what colour they are.

Can a dimmer even do 2 way ?

Sounds like you have messed up the connection, if it’s old colours and wired ‘Glesga 2 way style’ you should have the Red from the 3 core on it’s own in the common connection red from the 2 core with the yellow from the 3 core in L1 and 3 core blue and 2 core black in L2, probably.
Take a picture and we can see what the wiring is like!

The one for the downstairs room is wired up like instructions say, and that’s got two switches and works fine. Could it be different between the upstairs and downstairs and, given my reputation, will wiring it up differently and getting it wrong result in a huge fire?

get a multimeter on them to work out which is which.

… with the power isolated.

Well, I switched the wiring to what is was on the old one. There has been no fire yet. It behaves too, which is nice.

Whilst we’re on the subject of dimmer switches and fires……

I have a light fitting in my dining room which has 6 or so incandessant bulbs. The wiring is a standard single switch. I had fitted a dimmer switch, but every time one of the bulbs blew (frequently) the switch would get incredibly hot until you removed the blown bulb.

One switch melted and stopped working, so I replaced it, only for the same thing to happen and the switch actually set on fire. I have since replaced the dimmer switch with a regular switch without a problem.

Any ideas?

One switch melted and stopped working, so I replaced it, only for the same thing to happen and the switch actually set on fire. I have since replaced the dimmer switch with a regular switch without a problem.

Any ideas?

Nomex pyjamas and a robust escape strategy.

You have the wires the in the wrong terminals. Ignore all the stuff saying red should be in common etc. It can be any of the 3 colours as long as both switches are connected up the same. Put it back to how the old switch was wired, and if in doubt check how the other one us connected. This will solve the issue.

Pie face, you probably had too much power going through the dimmer. They are only rated to a certain amount of watts. If you exceed this they do burn out, although usually they just melt rather than actually set on fire. If in doubt take a lamp from your fitting to a wholesalers and tell them you want 6 dimmable LED vresigns of them, and a suitable dimmer.

my vote is on 6 incandescent bulbs (say 400w) is over the rating of the average dimmer switch, and the bulbs were blowing in such a way as to increase the amount of current flowing through them (rather than blowing and dropping the connection entirely??)