I have very old wiring : all black wires. A bedroom light did not work so I replaced the ceiling switch. The wiring at the switch and at the light was - 1 wire on its own and 2 wires joined. At the switch I put the single wire to common and the joined wires to L1.
Now the light stays on all the time and the other room lights work when the switch is in one position but not the other !

Hera, November 2010

crossed wires... your switch is not actually switching the light it should be but the ..loop live to the next switch and light ..a cct of light switches has live in and out untill the last switch.this has 1 live ...the light needs a switched live wire to be on and offable.the 2 joined wires at the light are neutrals the single wire ..switched live from the switch..The 2 joined wires at the switch should be live in and then out to the next switch , single wire goes to the light.

David Whitehouse, January 2011

you have mixed up the loop in loop out connections in the rose,get a spark in,you will never fix it without a test meter,

mm, December 2010

For the light to stay on all the time it is connected to permanent live rather than switched live - a wiring problem at the ceiling rose.

For the switch to have control over "downstream" lights it must be interrupting the looped (permanent) live that runs off to the other room(s) - a wiring problem at the ceiling rose.

Without any test or measurement equipment - and with all the wires the same colour - it may be best to call in an electrician.

To gain an understanding use Google - select Images - Enter ceiling rose - look at a wiring diagram.

Take care...

Peccavi, November 2010