Receptacle – How to Add an Always Hot Outlet to a Switch Controlling a Fan

Based on your description, it sounds like your wiring is this.

To wire the fan, you will need to remove the switched loop and convert it to a regular wire. So in the outlet box, disconnect the neutrals and hots. Wire cap all 3 neutrals together with a pig tail to reconnect the outlet, do the same for the hots. At the switch, remove the neutral from the switch and wire cap that with the neutral to the light. Then put the hot to the light where the neutral was on the switch. Like so.

I did not add grounds in the picture but they should be wire capped together in each box with a ground wire to the outlet and switch.

Yes, this should work. A few things you may have already considered:

1. Each time your cable goes into or out of a junction box you should plan to lose 6" in length.

   So tying into and out of the ceiling box for the fan would require 12" of slack on the existing 4-wire cable. Your plan to add a separate junction box is a better approach. The trick is to put it at least 6" closer to the dual-wired receptacle and run 3-wire the longer distance to this box. When you tie into the 4-wire here you will have extra 4-wire to use in the ceiling fan box.

2. Don't disconnect the red wire going to the duplex receptacle.

   Just tie red and black to the un-switched black in your junction box. This puts half the load on each wire and you don't have to rewire the receptacle in the wall.

3. Get a deep 2-gang switch box to fit all those connectors

   and dissipate the heat any dimmers you use to control fan speed or dim the fan lights. You're looking at needing at more than 29 cubic inches not counting extra for dimmers. And you always want to leave room for future expansion.

4. Get a ceiling box designed to hold a fan and mount it securely to a joist.