I have a dual switch downstairs in the hall, one switch controls the hall light, the other controls the landing light. The landing upstairs also has its own light switch which can be turned on or off.
I changed the switch downstairs to a new elegant looking one, I thought I had replaced the wires in exactly the same place however............. I now cannot turn the light switch on/off from upstairs and when I turn the hall light on, all of the lights go off upstairs !!
Confused... any help greatly appreciated.