A friend and I have been wiring up my new home (built 2012, neutrals everywhere) with Lutron Caseta smart switches (specifically in this case, PDW-5ANS-WH-A) and he was working on my guest bathroom and took apart the old switches before I got a look… and then he called me in because he was stumped:

There are two single pole switches, one for the light and one for the fan.

There are two ground wires — one each.

There is several neutral wires capped with a wire nut, not attached to the original switches as has been standard — I just add the neutral from the Caseta to the bundle (upgrade the wire nut if needed) and that's fine.

Then it gets weird: there are three left over black wires, not four. And there were wires directly between the two switches.

I ended up wiring the two red Lutron switches to one of them, and then the two black on the switches to one each of the remaining two.

I may have remembered that backwards, but regardless, it works, except that the light switch is now dependent on the fan switch. If the fan is off, the light switch doesn't work. And if you turn on the fan, the light turns on (default Caseta behavior after loss of power I believe) and can be controlled, but as soon as you turn the fan off, it also goes off.

I don't recall the original switches behaving that way, so is there a way to wire this so that they work independently?

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    This can be sorted out but you need to add to your question pictures or diagrams of the boxes with the wiring clearly. What you need to figure out is how many cables come into the box and how many wires in each cable, which cable power comes into the box on, which cables go to the fan and the light, and if there are any other cables, what they are (usually always-on line power for other receptacles or something.) – K H Apr 12 at 7:14
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    Can you provide some photos of the insides of the boxes in question please? – ThreePhaseEel Apr 12 at 11:42
  • In switch boxes the whites can be a hot sometimes (if fed from the ceiling). It is possible the hot(s) are coming from the ceiling, clear photos of the wires and cables entering the box will be helpful. The wire between the 2 switches was the hot that fed both of them. – Ed Beal Apr 12 at 13:56
  • If phase and neutral comes to the fixture, two wire cable is going to switch. Colors of regular cable is white and black. In that case the white wire is not neutral but returning phase. Simply measure resistance between white wire and ground if one has higher resistance , it is that case. – user263983 Apr 12 at 14:40

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