I'd like to solicit some opinions on what I'm dealing with here. I bought my duplex last year. By the entry ways of both units there are 3 gang single pole switches, one for the exterior porch light, one for the entryway light, and the other?
I've installed new recessed lighting in the living area and would like to use the unused gang so I don't have a dead switch and don't have to cut another hole in the wall.
I've only found two wires exiting the wall header in the attic. One is a 12/3 and the other a 12/2. The 12/2 goes directly to the entry way light. The porch exterior light must have been routed through the walls. The 12/3 wire is the supply. I'm not certain whether it makes another stop or whether it goes straight to the home run to the circuit box.
Here's what's strange. The black wire from the 12/3 is in series across all 3 single pole switches. The two known lights are wired as expected. But the third switch is wired to the red wire from the 12/3, thus when it is thrown, it connects red to black. What the heck is up with this? Both units are wired in this same exact manner.
Between black and ground with the circuit live, I'm getting 120v, but after disconnecting the red wire from the switch, I find that I get 25v between red and ground.
I haven't yet pulled the cover from the breaker box to try and figure out whether the red is actually connected to anything in there. Can anyone hazard a guess what the heck someone was trying to accomplish here? Is the 25v I'm measuring cross talk or something?
My idea, assuming that the red isn't actually connected to anything on the other end was to go up in the attic, and sever the 12/3 feed wire and route it into a jbox, and to splice the black/white/ground wires but to divert the red wire to a new 12/2 that will feed my new lights, leaving the red wire in the source 12/3 wire capped. Does this sound feasible?
Oh, there is also a 12/2 exiting the bottom of the box, which continues into the adjoining room, but I don't think that's relevant.
Here's a photo...