I am adding a ceiling fan to an existing junction box in my house. There was nothing there before, just a junction box which is rated for a ceiling fan. The house was built in 2016.

There is a standard switch that has Ground, a Line (live power) and Load wire going up to the fixture.

At the light fixture is the standard Ground, White, Black. But there is also a Red wire.

When the switch is off, both the black and red show ~2V (tested with a multimeter).

When the switch is turned on, the black wire shows 120V, and the red wire shows 12V.

There is definitely no red wire connected to this switch, so I am confused on why there is a red wire, and why it is showing 12V. Since it is in close proximity to the black wire, is it just picking up residual power?

  • 2
    The 12v is just phantom voltage. You have two parallel wires, one energized, one not connected to anything. The insulation isn't scientifically perfect, so there is a small capacitance between the wires. That is throwing some phantom voltage on there, but it's a trivial amount of energy and not useful for any work. You can only see it because you're using a DVM which is very sensitive and externally powered. It would not have enough oomph to move the jeweled movement in an analog meter. Sep 6, 2017 at 1:56
  • That's what I thought, but the reason I started down this path is that when I was wiring up the ceiling fan, something tripped the breaker. The switch was off as well so I am thoroughly confused. And I tested the wires with both a simple 'yes there is electricity' tester and the multimeter before proceeding.
    – esac
    Sep 6, 2017 at 1:58
  • @esac look for a nearby switch - normally one wire is for the Fan (Black) and the Other wire is for the Light (Red from the switch or Blue to the fan light kit). See my answer with pictures in about 5 minutes..
    – Ken
    Sep 6, 2017 at 2:50

1 Answer 1


Here is a picture of the proper wiring for a Pre-Wired Ceiling fan installation.

Ceiling Fan Wiring

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