Help with wiring on a single switch - two way!

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Hi prob something real simple for someone out there. I have a landing light with a switch either side of the landing and one at the bottom of the stairs. I just wanted to replace the light switch which was fine on one side on the landing as it was like for like and that is ok with me. However the other side must have an older switch on it. I have one cable coming from the top and one from the bottom, they both contain red, blue and yellow wires. The two yellows are connected via a choc block and the switch had two holes at the top labelled L1 where one red and one blue went into separately and the bottom had two holes labelled L2, once again one red and one blue went into these. The switch must be old, I am really not sure what goes where as my new one has L1, L2 and COM.

My initial instinct was to wrap the two that went into L1 together and do the same below but I don't think putting red and blue together would be right. Also I would then have nothing to put into COM! Please can somebody offer some advice, my daughter is crying as the landing light isn't on! lol
 
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that's an intermediate switch.. different beastie to a 2 way switch.. go back to the place you got it and see if they have intermediates in the same design..

electrics:lighting:intermediate:chockblock2w_i.gif
 
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Your new switch is the wrong type. You need an intermediate switch, which will have the required 4 terminals.

To fix this temporarily before you get a new switch, either put the old one back how it was, or if this is not possible, use the new switch and put both Red wires in the L1 terminal and both Blue wires in the L2 terminal. That switch won't work, but the others will.
 
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Thanks everyone, glad it wasn't me being stupid, well not entirely! I can change them as long as everything is the same, throws me when it isn't. I will put the old one back on for now. What is the purpose of the intermediate switch? Thanks
 
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S

sparkyspike

Have a look at the drawing above. An intermediate switch swaps L1 and L2 over. Effectively this turns the light on and off. So you can turn a light on and off from 3 positions, regardless of the positions of the other two switches.
 
S

sparkyspike

In the drawing, on the switches, the solid lines are the positions of the switch and the dotted lines are the new position if you flicked the switch up.

Electric current is going into terminal L1 of the top switch in the diagram (it comes from the red feed wire). Follow the wire which goes from L1 of that switch to the intermediate switch below. It then goes straight across the intermediate switch to terminal L2. Follow the red wire to the 3rd switch where it goes straight across to the C terminal. Then follow the yellow wire which goes through the intermediate switch via a terminal block, and to the C terminal of the top switch. This is where it stops.

But if you press the top switch, the current will be diverted to L2, where the black wire takes it to the light which comes on.

Anytime you press any switch, the light goes on or off, i.e. the opposite to what it was before.
 
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I can change them as long as everything is the same, throws me when it isn't.
Then please, please, please take the time to study how it works and acquire a genuine understanding of what's going on, or resolve never to do electrical work again. Bumbling around in the hope that what you need to know will fit with what you actually know could get you or someone else killed.
 

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