By Family Handyman | Updated: September 29, 2023
Wiring a 3-way switch can be more intricate than a traditional single-pole switch, but with our detailed diagrams and instructions, you’ll successfully wire a 3-way switch from a single-pole light switch. This guide provides step-by-step instructions, tools required, materials needed, and essential tips to make the process manageable.
Wiring a 3-way switch involves a more complex process than a single-pole switch, but the goal is to enable control of a light from two different switches. The entire project, including wiring diagrams, can be completed in a few hours, assuming no drywall removal and repair are necessary.
- 4-in-1 screwdriver
- Electrical tape
- Needle-nose pliers
- Non-contact voltage tester
- Utility knife
- Wire stripper/cutter
- 14-3 or 12-3 cable
- Three-way switches (2)
3-Way Switch Wiring
Wiring a 3-way light switch involves a unique configuration, allowing either switch to make or break the connection that completes the circuit to the light. Follow our 3-way switch wiring diagram for a successful installation.
Step 1: Directions for Wiring a 3-Way Light Switch Yourself
To add the switch, follow 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 3-way switch in the basement.
- Pro Tip: You may need to replace the existing switch box with a larger one to accommodate extra wires for the 3-way switch.
- Feed a length of 14-3 type NM cable (or 12-3) between the two boxes.
- Pro Tip: The 14-3 cable has three insulated conductors: white, black, and red (plus a bare ground wire).
- Connect the wires to the newly installed 3-way switches with ground screws using one of the two wiring diagrams (Fig. A or B).
- Pro Tip: The switches will be identified by a label on the common terminal, and/or the terminal screw will be a different color.
- Wrap black electrical tape around the ends of all white wires used as travelers between the 3-way switches.
- Pro Tip: This distinguishes these wires as “hot” and not neutral like most white wires.
Step 2: Wiring Diagrams
- Figure A: 3-Way Switch Wire Diagram — Power to Light Fixture
- Power enters the fixture box.
- The black hot wire connects to the far-right switch’s common terminal.
- Red and blue wires link the traveler terminals of both switches.
- The red wire, connected to the first switch’s common terminal, leads back to the fixture.
- Figure B: 3-Way Switch Wire Diagram — Power to Light Switch
- The incoming hot wire is attached to the first switch’s common dark-colored terminal.
- Two hot wires of the three-wire cable connect to brass-colored traveler terminals on each switch.
- The fixture’s hot wire connects to the second switch’s common terminal.
- Figure C: 3-Way Switch Wire Diagram — Power to Light Switch with Fixture Between Switches
- Power enters the fixture box.
- The incoming hot wire connects to the right switch’s common terminal.
- Two lengths of four-wire with a ground cable, joined at the fixture box, link the right and left switch traveler terminals to each other and to the fixture.
Successfully wiring a 3-way switch from a single-pole light switch requires careful attention to detail. With the provided diagrams and step-by-step instructions, you can efficiently complete this project, gaining control of a light from two different switches.