Here are the pictures, as requested: The light at the bottom of the stairs looks like There are three cables, all two conductors and the light itself. I will attempt to describe the connections. I'll call the top left cable as cable #1, the cable to its right cable #2, the bottom cable as cable #3. -white(1), white(3), and white of light wire nutted. -black(1), ***white(2)***, and black(3) wire nutted. -black(2) and black of light wire nutted. Switch #1 looks like: (I took lots of pictures, but none of them were really "easy to understand", like the fixture picture.) It looks like the bronze screw is in the middle and the adjacent screws are brass. Switch #2 looks like: It looks like the bronze screw is in the middle and the adjacent screws are brass. As far as I know, the job was professionally done. It works correctly, inasmuch as both switches can turn on the light. Given the age of the fixture, the style of the fixture, and the layers of paint, I would guess that this was the original fixture when the house was built. Does this help? I didn't do the voltmeter measurements, as I was confused by the instructions. Here are my guesses (based on other people's comments): 1) At the light fixture, the supply cable is the bottom cable. Cable #3, in my description. 2) At the light fixture, the cable going to switch #1 is the top right cable, Cable #2. 3) At the light fixture, the cable going to feed other things is the top left cable, Cable #1. 4) Normel pretty much summed it up in: "2 conductor cable is switch loop from the fixture; 3 conductor cable is between the two switches. This was my explanation way back in post #2." and "The white is not a neutral. You have the incoming hot and neutral at the light. The hot at the light is fed to the switch via the white wire, so the two wire cable is a switch loop. The screws where the two black wires attach are your commons." Texasredhead: The black wires are attached to each of the bronze screws. So, am I close in my guesses? Unfortunately, I have a followup question. I was looking at my book "Electrical code simplified house wiring guide, based on the 20th edition of the CEC and the BC admendments, 2006 to 2010" and saw this picture: In this picture, the middle switch shows the white wire going to the common terminal. Newbie/dummy question: Why is this diagram different from the way my setup is done? Am I missing something fundamental in my (mis)understanding?

The only way I can think of off hand to get a pseudo series circuit is if the wires are all pinched together behind the light fixture transfering some of the power. I doubt the wires are long enough to transfer that much voltage under normal circumstances. Unless the metal of the conduit is acting like a transformer, but the ground continuity would probably need to be broken or have a high impedance path back to the panel somewhere. This sounds more likely only because it is effecting all three wires at the same time, even when totally disconnected

Maestro dimmers aren't real 3-way switches. The master does all the dimming and switching work, and the different slaves just tell it what to do. (Don't you wish you could do that with your boss?) A little while back I was looking at a pair of these, but ended up going with a more conventional 3-way setup. In the process I bookmarked this website, which shows how to wire them. Maestro Wiring I hope it doesn't confuse things if I say that rather than alternating red and black as that diagram shows, I would have used the black wire in the 14-3 NM to connect the master and slave units in series, and then black from there on to the light. To link the blue dimmer terminals, I would have re-identified the red wire in the 14-3 NM with blue tape.

I'm a total amateur but it does seem a bit unusual for SWITCHES to all have two sets of wires. Usually power goes to the device being switched, then down and back to the switch, so there is only one piece of Romex coming into the switch. I doubt disconnecting one will be a good idea, it's that way for some reason. You can verify whether it's actually two hot wires, or as randy said above, the second is actually carrying power to down the line. Shut off the breaker, disconnect one set of wires from the switch so they are not touching the other set (or anything else!), turn the power back on and check the voltage on the two sets of wires. I suspect you will find one set is hot and the other is not. In which case, don't mess with what isn't broken.