Wiring a three-way light switch
Wiring of 3-way light switches is certainly more complicated than that of the more common single-pole switch, but you can figure it out if you follow our either of our 3-way switch wiring diagram. With a pair of 3-way switches, either switch can make or break the connection that completes the circuit to the light. The whole wiring a light switch project can be completed in a few hours if you don’t have to do any drywall removal and repair. Keep reading the 3 way switch wiring diagram to learn light switch wiring.
To add the switch, you’ll use one of two wiring a light switch diagrams, depending on whether the power comes to your light switch first (the most common situation) or to the light fixture first. Either way, complete these five steps for 3 way light switch wiring:
- Turn off the correct circuit at your electrical panel.
- Add an electrical box for the second three-way switch in the basement. It’s likely you’ll also need to replace the existing switch box with a larger one to accommodate the extra wires for the 3 way switch.
- Feed a length of 14-3 type NM cable (or 12-3, if you’re connecting to 12-gauge wire) between the two boxes. The 14-3 cable has three insulated conductors: white, black and red (plus a bare ground wire).
- Connect the wires to the new three-way switches with ground screws using one of the two wiring diagrams (Fig. A or B). The switches will be identified by a label on the common terminal and/or the terminal screw will be a different color.
- Make sure to wrap black electrical tape around the ends of all white wires used as travelers between the three-way switches. If you have the setup shown in Fig. A, also wrap black tape around the white wire from the switch to the light. This way, both you and others will know these wires are “hot” and not neutral like most white wires.
Caution: If you have aluminum wiring, call in a licensed pro who’s certified to work with it. This wiring is dull gray, not the dull orange that’s characteristic of copper.
Figure A: 3 Way Switch Diagram- Power to Light Fixture
This 3 way switch wiring diagram shows how to do the light switch wiring and the light when the power is coming to the light fixture.
Figure B: 3 Way Switch Diagram- Power to Light Switch
This 3 way switch diagram shows how to wire the switches and the light when the power is coming to the light switch.
Required Tools for this 3 Way Switch Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
- 4-in-1 screwdriver
- Electrical tape
- Needle-nose pliers
- Non-contact voltage tester
- Utility knife
- Wire stripper/cutter
Required Materials for this 3 Way Switch Project
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.
- 14-3 or 12-3 cable
- Three-way switches (2)