Screwed up wiring?

[srv52761]

When I checked the voltage all wires were disconnected from the switches. No, I didn't check the white to ground I can do that if you still think it's pertinent.

I don’t think you have a ground wire in there, do you?  Any green wires?

[Scouter]

Scouter,  check out the diagrams here -  https://blog.smartthings.com/how-to/how-...ht-switch/  power into light - power into switch.  If yours is wired power into light,  I agree with TDKPE you may not be able to use the humidity switch.

Yeah, I figured that, will have to find a way to pull new wires through.

What has thrown me is the white (neutral) wire coming from one switch to the other. I can't wrap my head around how it's working. Why not just use the white wire that's part of the romex from the second switch? That is cut off inside the box.

[Scouter]

This seems to be it.  Except for not coding the white, this is the way I was taught; if using a two wire assembly for the switch loop the final wire to the fixture was supposed to be black.

Edit: so you have three conductors in the box; two black, one white?  Plus a white jumper from one switch to the other?  
If so, you may have two runs of romex, A and B.  They used the white from A to supply power to the switches, jumping from one to the other.  They cut off the last 6” of the white from B and used it for the jumper, may not even be in the box.  They used the black from each to run power to the fixtures. The neutrals are still in the light fan box.  Bet the white from B is cut off in the fan box also. 

If you look in the box and see even 3/4” of the truncated white, you may be able to pigtail it with a Wago connector, they only need less than 1/2” stripped.    If that is true at the fan, you will have your neutral wire.
You may have to pull the switch box to work on the wire, then use an old work box as a replacement, but it may be easier than running a new circuit.

By Wago, you mean this:

https://ledlam.co.uk/wp-content/uploads/...OR-02.jpeg

I've used Tyco's version (push connectors) before. Problem is that the white wire from B is cut flush with where it is entering the box, not even 1/2" to work with.

[Scouter]

I don’t think you have a ground wire in there, do you?  Any green wires?

One, from Switch 1, everything other than the black wire to Switch 2 is cut about 1/2" on the inside of the box. They grounded Switch 1 but not Switch 2. As I said, a real SNAFU job.

[srv52761]

Yeah, I figured that, will have to find a way to pull new wires through.

...... That is cut off inside the box.

See my previous, you may not have to pull a new wire.

Addendum to my previous:
By pulling the current switch box, you can prep the truncated white wire then replace with an extra deep old work box to capture the pigtailed white.  
If it is not deep enough, you may be able to “make it deeper”  by adding an extension ring.  They make a newer box that can be used as an old work or new construction box.  It screws into the stud with angled screws, similar to a Kreg jig.  You could set it deeper with an extension ring.  Then similar at the fan, and bring in the neutral from the fan box.

[TDKPE]

Sadly, I can't check the wires to the fan without busting open the plaster ceiling, there is no other access. They created a drop-box from the ceiling in the tub area, no access to the actual wiring.

Are you sure?  Did you dismantle the interior of the fan?  Some have a junction box on the inside, buried behind sheet metal.  Might have to remove the motor first, which is usually only held in with a couple of screws with the motor plugged into a receptacle.  That receptacle is probably where the j-box is.

Worth a try at least.

[srv52761]

Alternately
In wall slice kit

I have never used one.  Maybe a sparky can verify if it conforms to 334.40(B)

[Scouter]

See my previous, you may not have to pull a new wire.

Addendum to my previous:
By pulling the current switch box, you can prep the truncated white wire then replace with an extra deep old work box to capture the pigtailed white.  
If it is not deep enough, you may be able to “make it deeper”  by adding an extension ring.  They make a newer box that can be used as an old work or new construction box.  It screws into the stud with angled screws, similar to a Kreg jig.  You could set it deeper with an extension ring.  Then similar at the fan, and bring in the neutral from the fan box.

I'm not sure what you mean by "prep the truncated wire", since it is cut at the box I can't see a way of pigtailing it except outside of the box, and that's not allowed. Can you explain further?

[EricU]

there's always the possibility that someone didn't understand what was going on in there and misinterpreted.  And it barely works.

[Scouter]

Alternately
In wall slice kit

I have never used one.  Maybe a sparky can verify if it conforms to 334.40(B)

That's a thought, if I can figure out how to get the old wire connected. Unless they have some run loose inside the wall there isn't enough to work with unless I bust open the wall.