by ericmark »
Wed Mar 19, 2008 5:17 pm
Seems your lights are wired in parallel not as a two way light. Be careful looking at two way lights. Wikipedia shows them wired in school boy fashion which although it works requires wires to be joined inside the switch box. Most electricians instead of taking live to common and switch from common swap the switch around and common is only wire not connected to lamp or line. Unless you are into logic you will get totally confused without a diagram. What you have found is common where upstairs and downstairs have been split onto different fuses. Since both switches had a permanent live on one terminal instead of running triple and earth between the lights they ran twin and earth and bridged the live in one double switch. Where this has been then split up and down this practice had to stop as the two lives were from different fuses/mcb's and it would result in the wrong return wire being used. To correct this often the only way is to fit a new cable. To correct, both switches would need rewiring. If you find red, yellow, blue cores to one of the cables in the switch (it will go between both switches so can be viewed in either) then maybe it can be corrected without running new cables but if only red and black cores to all cables it would take a lot more work. Either way I would not think it would be DIY work.
