Electrical – Mixing 18awg wire and 16awg wire on a ceiling fan installation

You are not wired the same way as the picture in your instructions. I think the power comes in to the ceiling box, and the switch is a separate cable.

To verify this, disconnect all of the wiring in the ceiling box and at the switch. Turn the breaker on and carefully check for voltage between the black and white wires. When you find the black and white pair (or just the black wire if you are using a voltage tester) that has power, then you can turn the breaker off.

If this test confirms voltage on just one black wire, then connect as follows:

1. In the ceiling box:
   • Connect the black powered wire to the other black wire in the ceiling box.
   • Identify the white wire that is paired with the black powered wire. It will be in the same cable sheath. Connect that white wire to the white wire on the fan.
   • Connect the remaining white wire (which would be coming from the switch) to the black wire on the fan/controller. Wrap a piece of electrical tape around the white wire about a half inch back from the wirenut. This will signify that the white wire is carrying live current and is not a neutral.
2. In the switch box:
   • Connect the black wire to the switch wire with the yellow sticker.
   • Connect the white wire to the switch wire with the blue sticker. Also mark this white wire with electrical tape.

Someone took a dangerous and illegal shortcut to separating the fan and light switches. Rather than running a second hot, they're using the white as a hot and the ground conductor as the neutral. You should rectify the situation immediately by returning the white wire to service as a proper neutral. We can help further if you describe or post a photo of the switch wiring.

Your final comment about having no neutral in the house makes sense if you're confusing neutral and ground. Older homes commonly have ungrounded branch circuits. At the switch, you probably have blacks and whites, but no bare grounds. My guess is that the ceiling light box was added after the house was built using contemporary 14/2 with ground. Since the ground didn't have a function, it was converted to be used as a neutral for a split switch scenario.