I have a 4 season room with some lights but the switch is in the kitchen. I installed a 2-gang box in the room and ran a 3-wire romex wire from the new box to the existing box (they are on the opposite sides of the same wall), and am trying to connect it in a 3 way configuration so I can turn the light on or off from either switch.
Below is a photo of the existing box in the kitchen. A1 and A2 were connected in a single pole configuration. B1, B2, and B3 are from the new wire going between the boxes. When I turn the power on and test the wires with my non-contact tester, the white wire A1 is live and the black wire A2 is not, which I was not expecting. I can't seem to get the wire configuration right so I'm hoping someone can tell me how to wire these up properly. I'm using Legrand Adorne paddle switches (instructions here). Thanks in advance.