Another 3 way Mess
It is just a series circuit made up of a source, a load, and a composite switch made up of two switches. It still just turns a light on and off.
Pick a 3 way schematic and a wiring diagram that allows you to most closely follow the existing wire schematic, routing and colors. There are three wiring diagrams that I know of; the light at either end of the chain, or in the middle.
Ignore wires that are just passing power onto other circuits, assuming you can figure out which wires these are. This involves figuring out which way the power is flowing and this is not as easily done as with DC circuits.
With some of these setups, worked on by who knows who in the past, it may be possible that it is not possible to salvage what is there, but you don't dare start randomly disconnecting wires, either.
I'd do what I can with the power off, an ohmmeter, and an extension cord to bring the ohmmeter leads to where you need them, but first draw what you see in each box so at least you can return the setup to the previous state, imperfect as it may have been.
To use the ohmmeter you need to disconnect wires and unscrew the bulb.
Wait till you try to debug 3 or more switches controlling the same light!
Last edited by Yoyizit; 02-11-2009 at 03:03 PM.