I have a 3 switch in my hall controlling downstairs hall, porch light and upstairs landing. The upstairs landing is also controlled by a switch on the landing, this does not however control the downstairs hall light. The downstairs hall light is also controlled by a 2 switch downstairs which also operates the downstairs WC.
My problem is I tried to replace the switch and caused a short. I then tried to rewire and got it wrong.
The cables within the switch are labelled switch, up, down and one blank.
All the Earths are together.
Is there any standard way anyone can give me advice on re wiring this switch.
There is no hard and fast rule as to how to wire two way switches. Normally switch and line go to L1 and L2 on either switch but not both and also L1 to L1 and L2 to L2 and Com to Com between both switches. With non two way wiring L2 is normally not used with switch and Line going to L1 and Common. If wired strictly to rule book all wires would be same colour either red or brown according to age of wiring this is hardly ever done and cable with red yellow blue or Brown Black gray is normally used between both switches but since the is not strictly to rule book there are no conventions as to which colour is used for which.
Firstly I'm going to assume that you have a standard loop in plate lighting circuit and that its using the older wire colours.
If you look behind the plate there should be 3 cables coming in.
There will be 1 twin and earth cable and 2 - 3 core and earth cables.
Firstly lets sort the easy one out. Take the twin and earth and wire the red to the COM of the switch you want to work the porch light and put the black to the L1 terminal of the same switch.
Now you need to find out how to wire up the 2 way switches. Firstly you'll need to go to the upstairs landing switch or the other downstairs one and take the switch off. Look to see where the 3 colour cores have been put. In my experience its red to COM, yellow and blue to L1 and L2 (either way about) but theres no hard and fast rule. Once you find out which way they go in the existing switches match it at the one you are wiring.
Now your good to test. If you find the light switch is working the wrong way around then swap the wires in L1 and L2 over.
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