how to trace mystery wires in old fan box?

[General_Valeria]

Pulled out an old fan/light combo and now I'm staring at an 8-wire junction box that doesn't make much sense. Two blacks and two whites are hot, but the other four wires are dead no matter what I do with the switch. Setup used to be for a fan/light with a remote, so it was basically always powered. Now I want to run it off a normal switch. Anyone run into this before? I'm guessing the "dead" wires were part of the fan's old remote control wiring, but I don't want to assume and hook it up wrong. How do you usually trace this kind of mess to figure out which are actually safe to use for a switched leg?

 

[PGB1]

I'm not a residential guy, General, but I'd probably de-energize everything in the box and use a Tone Generator. Check all boxes in the room to find the unknowns. Careful- The boxes you open may have energized conductors in them. (At work, everything is in pipe so the job is much easier with a Wire Sorter. If your house is piped, this would be the quickest way.)

Klein makes a very good tone generator with a strong signal for about 80.00 USD. There are also no-name ones for far less. Samples are below.
Paul

 

[VoltagexV]

@General_Valeria, I second using a tone generator. The dead wires you're seeing were the switched loads that the fan's remote receiver was controlling. The two hot wires were simply supplying constant power to that receiver. Using a toner is the quickest and most effective way to trace those dead wires back to the switch box without having to open up every box in the room. Just make sure the power is off before you clip the toner to anything like @PGB1 said. Once you've identified the correct switched leg, you'll be able to wire up your new switch and fixture properly.

 

[electr0roy]

@General_Valeria
The 8 wires represent two separate runs of wire, giving a constant power feed and an unused switch leg that was intended for a separate light/fan control.
The safest way to trace this mess is with a multimeter/continuity tester (breaker OFF). You need to go down to your wall switch and see which wire leaves the switch and runs up to the ceiling. That is your actual switched leg.
It will be one of your currently 'dead' wires. Twist the wires together at one end (e.g., switch end black to ground) and test for continuity at the other end (ceiling box) to figure out which is which.

 

[Carrot_]

hi @General_Valeria before you run the continuity test, check the unused wires. On a standard 14/3 cable, the red wire is the intended switched hot.
your original setup used a remote, so the installer might've ignored the red wire or used it for the fan's constant power. Focus your continuity test first on the red and the remaining black wires to find your true switch leg