How to Wire a Three-Way Light Switch

Introduction

Wiring a three-way light switch allows you to control a light fixture from two separate locations, like the top and bottom of a staircase. While it may seem complicated, wiring a three-way switch is relatively simple if you follow these steps.

What You'll Need

Before getting started, make sure you have the following materials:

• Two three-way switches - Specifically designed with three terminals to allow connecting the traveler wires.

• Electrical box for each switch - Make sure they are large enough to fit the switches and wires comfortably.

• Light fixture - Such as an overhead light or ceiling fan you want to control with the switches.

• Power supply wires - Live wires bringing power to the switch setup.

• Romex electrical wire - To connect the switches and light fixture.

• Wire connectors - To join the wires together.

• Voltage tester - To safely check for live power.

• Screwdriver - For connecting wires to switches and light fixture.

• Electrical tape - For covering splices as an extra safety precaution.

Turn Off Power

Before touching any wires or doing electrical work, turn off the power supply at the circuit breaker. Ensure power is off by using a non-contact voltage tester on the wires. Working with live electrical wires can result in severe shock or electrocution.

Install the Light Fixture

If you're wiring in a new light fixture, start by installing it in the desired location and connecting the black (live) and white (neutral) wires, along with the ground wire if applicable. Leave the end of the Romex cable free to connect the switches.

Connect the Power Supply

Run Romex cable from the circuit breaker panel to one of the light switch boxes. Insert the cable through the knockout hole and secure it with a cable clamp. Connect the black (live) wire to the common terminal on the 3-way switch and the white (neutral) wire to the neutral terminal. The ground wire should also be connected to the grounding terminal on the switch box.

Run Cable Between Switches

From the first switch box, run a 3-wire Romex cable to the second switch box location. This will be your travelers' cable, so leave the ends free for now. Run the cable through knockout holes and secure with clamps in each switch box.

Connect the Traveler Wires

Taking one switch, connect the black (live) wire to the common terminal and a red or other colored wire to one of the traveler terminals. On the second switch, connect the same colored traveler wire to the "common" terminal. Connect the other traveler wire to the remaining traveler terminal on each switch.

Connect Switches to the Light

Run a 2-wire Romex cable from the second switch box to the light fixture. Connect one wire to the common terminal on the second switch and the other wire to the open traveler terminal on the first switch. Connect the other ends of the wires to the fixture, matching black to black and white to white.

Finish and Test

Secure and close up all the wire connections with wire connectors. Attach the switch plates and turn the power back on at the circuit breaker. Test that the switches work to successfully control the light fixture. Flip one switch on and the other should turn the light off. Congratulations, you have now wired a three-way light switch!

Frequently Asked Questions

What is a three-way switch?

A three-way switch has three terminals to control a light fixture from two separate locations. There are two switches that work in tandem to turn the light on and off.

How does a three-way switch work?

Three-way switches use traveler wires to pass power between the switches and light fixture. When the switches are opposite, power flows through to activate the light. When they match, the circuit is broken and the light turns off.

What wires are needed for a three-way switch?

A three-way switch requires a three-wire Romex cable between the switches (live, neutral, traveler) and a two-wire cable from the second switch to the light (switched live and neutral).

Can I use a regular single-pole switch?

No, you must use specific three-way switches designed for this kind of wiring setup. Single-pole switches have only two terminals and won't work properly.

How do I troubleshoot a three-way switch not working?

Check all connections and make sure the traveler wires match up properly between switches. Verify the power supply and cables have continuity. The travelers may also need to be reversed if the switches are not operating correctly.