I have two light bulbs controlled by three light switches. I replaced two of them a while ago (can't remember what the wiring looks like) with no problems. However, I encountered the following issue when attempting to replace the third light switch. The diagram belows shows the old one on left - the new one, to be installed, on the right :

Wiring diagram of light switches, current on left new one to be installed on right

Any advice on how to wire up the new switch ? The red lines show a connection outside of light switch and earth I have not included, it is also outside of switch.

The two lights themselves are both either turned on or off, ie I can can turn both on at one end of hallway and then walk along to other end (or the middle) and turn both off - they work as intended. But I have no idea how to wire up the new switch, is it even the right type of switch ?


2 Answers 2


That's a 4 way switch, not a 3 way switch (your replacement device is a 3 way). That switch is in the middle of the chain, and you need to replace it with another 4 way switch.

I found a tutorial on 4 way wiring here: http://www.wfu.edu/~matthews/courses/p230/switches/SwitchesTut.html

  • +1 for the same answer, I was even going to use the same link!
    – BMitch
    Commented Dec 12, 2011 at 12:28
  • my replacement device is called a 2-way on the box, the com hole is for common wires (the two reds) ? Commented Dec 12, 2011 at 12:29
  • 1
    in fact, I can't see a 4 way light switch advertised anywhere (the high street uk diy superstores) Commented Dec 12, 2011 at 13:09
  • 3
    @NimChimpsky In the UK they may be called 3-way switches. Either way the switch you need will have 4 terminals (+ground), not 3.
    – Tester101
    Commented Dec 12, 2011 at 13:19
  • Right, as Owain's answer says, in the U.K. they're 2-way and intermediate, and the red, blue and yellow wires in the OP's diagram, plus the L1, L2 labels were a giveaway that the OP is in the U.K., or India. :) Commented Sep 25, 2016 at 5:38

In the UK a 2-way switch is used for switching a light from 2 places. It is called 2-way because there the Common terminal is switched to one of two L terminals.

The middle switches with 4 terminals are called 'intermediate' in the UK.

eg http://www.tlc-direct.co.uk/Products/MKK4875.html

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