My girlfriend has a rather unusual wiring setup in her home with a two way switch at one end of the room, and a three way switch at the other end.
When the two-way switch is in the down position, the three way switch does nothing at all. However, when that switch is in the up position, the three-way switch works as normal.
I have pulled both switches out and at the end of the room with the three way switch I found that it has the standard setup for a three-way; one white, one black, and one traveller. There are no grounds, as the home was built in the 1950's.
At the other end of the room, in the box for the two-way, there are 2 black wires. I am assuming one of them goes to the light, while the other seems to receive power from the three-way switch, because when the breaker is on, and the three-way switch is in the down position, neither black wire is hot, but when the three way switch is in the up position, one black wire becomes hot.
Can anyone help me out by explaining (or providing a wiring diagram of) the most likely way that this is wired?
I realize that without going into the drywall and attic, it could be done multiple ways, but seeing as this is not my home, and she is renting, I cannot go into the drywall. I did try checking the attic, but there is too much of the original insulation in the way to try to get to the light.
Edits for clarity:
1) I will try to get pictures this weekend
2) There are two switches total controlling the light. One is single pole (this is the one I previously called two way), the other is a three way switch.
In the box for the single pole switch are two black wires connected to the switch and two white wires which are connected to nothing. One is capped off and the other is cut off at the entrance to the box.
At the bottom of the three way switch is a twisted pair of wires, one black one white. At the top, is a single black wire.
I previously assumed the single black wire was the traveler but I'm beginning to think it is not.
I will bring a volt meter and electrical tester with me this weekend and provide those details along with the pictures.
Best Answer
A standard three way setup has a hot feed or a switched leg to the load, and two traveler wires between the two switches. One switch gets a hot feed and the other gets the switched leg to the load.
The "two-way" switch you describe is a single pole switch and does not belong in a three-way switch loop. That is why the circuit does not work properly.
The problem with giving you a diagram is, there are several different ways to wire this circuit depending on where you feed the circuit. So, you need to determine where the circuit is fed from. The light or one of the switches are your choices.
Search the interwebs for "three-way switch circuit" and you should be able to find all of the several iterations of this circuit.
Good luck!