Electrical – 14 Ga stranded wire bathroom fan/light on 20 Amp circuit

It sounds like you have or had knob and tube wiring that might have been converted,
which consists on a Hot and a Neutral With no Ground (which is needed for GFCI, but

sometimes use the Neutral pigtail to mickey mouse false ground,).

*You can add a ground with a wire to copper pipe from sink’s water supply or run to basement)

14-2 wire is rated at 15 amps MAX

12-2 wire is rated 20 amps MAX

If you splice or run off a 14 Gauge to a 12 Gauge you must treat it as a 14 gauge

The higher the gauge the smaller the wire weakest link being 14 while using 14 to 12

If you are rewiring the whole bath and rooms then 12 gauge is the sanest answer

12 Gauge handles 15 or 20 amperes 14 should not be more than 15 for safety reasons

(When using 12 on 20A breaker use screw terminal as opposed to tension insert)

Testing for a hot wire when there is no labeling on wire casing (sheath) use a meter on ~ AC

And use a ground from ground cold water pipe and then touch pos lead on each wire (they do sell polarity test tools also don’t always work with conversion wiring)

The 110 – 120V reading wire is the hot

Hope that answers your question.

Sincerely BEAR

Sounds like you have one black hot wire coming into the box (probably that bottom one), which passed through a hot over to your bedroom switch.

So my guess would be that you should have two of the blacks wirenutted together -- that would be the hot wire coming in to the box, and the passthrough to the bedroom light. Also in that bundle should be two pigtailed wires that go to one pole of your 2 switches.

Then the other pole of the switches would be connected to the remaining black wires. The white neutrals should remain bundled together as they are.

It looks like the ground wires also have loops in them for connecting to screw terminals, you should make sure that all of the ground wires in the box are connected together with a wire nut so you have an uninterrupted ground even if there are no switches connected, then pigtail off of that bundle to connect to the ground screw on your new switches.

Here's a diagram showing my guess at how the hots should be connected:

Though this is only a guess -- an easy way to identify which one is the hot wire would be to tape or wirenut the exposed ends of the wire and leave them hanging out of the box, turn on the breaker, then use your non-contact voltage sensor to see which one is hot.

There's no easy way other than trial-and-error to identify which ones go to each bathroom light and which one goes over to the bedroom.

Oh, and do remember to connect the ground to the new switches since you have a plastic box (even if the previous switches were not grounded) - I think it's required by code now, but even if not, it's a good idea - especially in a bathroom where wet hands will be touching the light switch.