On the S1 side. Is there any voltage between the Black and the floating White?
Yes, if I measure on the S1 side between the black connected to the switch and the floating white, that measures 110v.
If your diagram is correct. It looks like the Line was routed to common S1 and then the two travelers went to S2. From S2 common the line goes into the lights line input. The neutral for the lights seems to be only in the lights.
That is correct. When I took the light apart, it seems like the box under the light is also being used as a junction point for some other electrical connections in which there is a 110v line coming to that box. I tried verify 110v at the light, but the way things were stuffed in that box and taped, I didn't want to rip that all apart and have to redo all the electrical tape, but that is where the light was getting it's neutral connection.
When I looked in the box for S2, I saw all the ground wires tied together. I took out the ground wire for the traveler wires and was going to put heat shrink tube on it and use that as the control wire. So I went to the box for S1, they CUT the ground wire for the traveler right at the edge of the box so there is not enough room for me to even wire nut an extension on it. Not to mention, all the wires coming to the box are JUST long enough to reach the switch. All the casing for the wires is cut to the edge of the box and there is no slack in any of the wire inside the wall for servicing it if there was a problem. I tried pulling on the wire in the box to see if there was any stuffed in the wall, but there was none. I am a firm believer that when doing ANY kind of wiring, that a service loop is left in the wire so there is at least some slack for things like this.
My thought is that I will connect the light in the ceiling with an inline module. Then get some A series XPT switches for the wall boxes with XP1A switches.
Any way I go with this means a trip to the attic to mess with the box that the light is connected to because there is no room in the box or in the fixture for me to put the inline module. I wonder how bad the other switches are going to be....
Dan B.