3-Way Switch Wiring Diagram Variation #3 : Electrical Online Wiring diagram for a 3-way switch, one of the many wiring diagrams showing different methods of wiring a three way switch circuit. This electrical wiring diagram shows power into light switch Box #1 – wire to light from switch box #1, and from switch box #1 to three-way light switch box #2. Wiring A 3 Way Switch? - Easy Do It Yourself Home Improvements Wiring a 3 way switch with the power coming in through the light and flowing to the switches. Be sure to mark the white wire as noted so if any future repairs or replacement is needed, whoever goes into the box will know it is marked as a hot wire.