Right in the middle of this job and realised I don't know what I'm doing. I'm in the UK.

I currently have a Crabtree switch (which I believe is called a single gang two way switch) on a light on my living room. The switch had three wires on it which feed into terminals on the switch labelled: L1, L2 and L3

However on my new Crabtree dimmer switch the terminals are labelled as:

L1, L2 and a then a wavy line with a diagonal arrow through it pointing to the top right.

Can anyone please explain how I should wire the new dimmer in? Should L3 now go into the terminal with the wavy symbol?

Any help would be really appreciated as I don't want to blow anything up.

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    – FreeMan
    Jul 30 '20 at 14:04

You have three wires because its a two way (or more) switch; You will find your light is switchable in two (or more) locations.

The wavy line with an arrow is the 'load' terminal, meaning this should be connected to the light; either directly or though the other switch(es)

enter image description here

It is likely that the old L1 goes to the load; the other two won't matter.

To be sure, you need to test that the wire does indeed go to the light; this will require some electrical test equipment, and may require testing live circuits, so it shouldn't be done without some experience.

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