So I've been installing a ceiling fan and I'm encountering an issue I didn't come across in 2 other rooms, same fan model etc. At the ceiling box I've got Ground, Neutral, Red, and Black. In the other rooms I've been able to wire the light to the switch and the fan motor/remote to constant power no problem to keep them separate. I want to be able to run the fan without the light at night. Here, while I am able to get the light working off the switch (black wire), I am unable to get the fan running off the constant (red wire.) When I put my multimeter to the switched wire in the ceiling (black), I get 120V when the switch is on. Red wire has .5V with the switch off and 15V with it on (?) I looked in the box behind the switch and I've got a loose red wire in there capped off. Is that my problem? Seems like maybe it was wired for a fan but not connected? How could I make this work? Do I need to wire nut the red to another wire in the switch? Thanks in advance.
UPDATE: Ok, so I flipped the breaker labeled for the bedroom lights which also includes the hallway light (share walls with the dining room) and THAT is now killing the switch and the fan successfully. Weird. Is this what's called a multi-wire branch circuit (MWBC)? Should I make sure to also flip the breaker called Dining Room since that was successfully shutting off the power to the light in the fan (but not the motor)? Bottomline, I don't mind adding a note on the breaker box to remind myself or whoever, but is is safe? Thanks.