too many wires

[BuzzLight]

I am currently installing a one way one gang dimmer in my bedroom but when removing the previous switch I notice that there are three wires attached to the switch, black and red (expected) and blue (unexpected).

Does this mean at some time this was used as a two way light. There is no sign of this in the house?

The current switch works but has the blue switch attached - C-Red, L2-Black, L1-Blue. On my new dimmer I have a live, load, slave and earth. I can attach the blue to the slave I guess but can I just remove this wire. There was some wall lights previously and I wonder if they were attached in some way.

 

[Lectrician]

Put it back as before. Slave is com.

If it worked OK before, I don't see the point disrupting anything.

 

[pna]

Could have been 2 way lighting - switch by the door and another accessible from the bed - was there a ceiling lightpull that could have been removed ?

 

[Lectrician]

The colours don't make much sense really.

Red and black in one sheath, does the blue have a sheath??

 

[felix]

Perhaps that blue wire once went to the wall lights. This would have been a rather odd arrangement in which the wall lights went off if you turned on the main light. I suggest you remove the blue wire from the switch and insulate it, preferably by putting its end into a choc block. If some light somewhere no longer works, this will be a clue to the purpose of the wire. My guess is that it's redundant and nothing will change.