Replacing a one way light switch with 2 two way light switch

[pvurgest]

I have followed the instructions on this site to install a new two way system which replaces the old one way system in my kitchen. The original swith had Comm, L1 & L2. There was one red wire in Comm and two red wires in L1. I worked on the assumption that the two red wires in L1 had the same function as the black would have and connected the new 3 core and earth wire accordingly. Now - both switches operate the light fitting but if I switch on at one switch, I can't swich off at the other. I am sure it must be my wiring. Please help

 

[Inspector]

Sounds like there was something rare with the wiring before you started.

At what terminal on one of the light switches do you have the permanent live cable terminated.

I ask this because ...
You should have a single red cable (permanent live) from the ceiling rose to COM on switch No1
You should have a twin red cable between the two switches (terminated on L1 and L2 on both)
You should have a single red cable returning to the ceiling rose terminating in the switched live position (in the same terminal as the brown wire of the pendant light fitting)

So it looks like this

L1o---------------------oL1
Perm Live----oCOM COMo--------lamp supply
L2o---------------------oL2

So the way it works is ...
Assume you lights are OFF, the supply comes to switch No1 and you make a choice of sending power (by switching) down a core of the twin red.
eg Perm Live - COM - L1(on switch 1) - L1(on switch 2) - COM = Lights ON

 

[pvurgest]

Thanks. I have sorted the problem now. You were right. I had connected the new red wire (from the 3 core & earth) to L1 on the original switch. I have now switched two red wires around so that the new red wire is connected to com on both switches. My mistake, but problem solved. Thanks