Well first of all, was the original can a remodel can or was it a can that had hanger bars but were removed? Remodel cans just sit on the drywall.OK, redoing a room that has one can light on a switch. Found out it didn't have the hanger bars, it was just sitting on top of the drywall. Perfect. So, I bought a new light to get the bars, then I was just going to replace the whole thing instead of taking one apart for the other. Wife also asked me to add a second one in the room.
The new light has 3 wires (B, W, Cu) with push connectors already on them. I think that I'll just take the existing wire, cut off the old light, push the wires into the connector, and then use some extra wire to run to the next one, sound right?
Couple of questions:
1. The push connectors have 3 empty holes, doesn't matter which one for which light, right? I figured they all just get connected together.
2. In the instruction booklet, it says: "If fixture is to be switched from wall switch or dimmer, make sure black supply wire is properly connected to the switch or dimmer. DO NOT connent the white supply wire to the switch." I can't see how the switch is wired (can take apart if needed), and wasn't sure what this meant. If another can light was already working on that switch, is it safe to assume that it's already OK?
Just be careful not to cut off too much wire. If the wire doesn't reach the new can then you would need to splice in a junction box.
As for your other questions:
1. They include three holes so you can easily pigtail. One wire comes in for power/neutral/ground and the others can run to the other light from one of the other holes.
2. This is so you don't do a switched neutral. The light switch would function but it isn't the ideal way to do it and can be a safety hazard. You can tell if its a switched neutral by measuring at the can the black wire and seeing if the voltage on the black changes when you flip the switch.