How to Wire a 3-Way Switch

Introduction

Wiring a 3-way switch allows you to control a light fixture from two separate locations, like at the top and bottom of a staircase. 3-way switches require a 3-wire cable between the two switches that allows electricity to travel in both directions. With some basic electrical knowledge and supplies, wiring a 3-way switch is an easy do-it-yourself home wiring project.

What You'll Need

Before wiring a 3-way switch, make sure you have the following materials:

Two 3-way switches - Specified on the packaging as 3-way or 3-pole.
3-conductor cable - This has three insulated wires and an uninsulated ground wire. Often called 14/3 cable.
Wire connectors - Also called wire nuts, these twist the wires together.
Voltage tester - To confirm the power is off at the circuit breaker.
Phillips screwdriver - To remove the switch plate covers.
Needle nose pliers - Makes manipulating the wires easier.
Electrical tape - Covers junctions and bare ground wires.

Turning Off Power

Before wiring a 3-way switch, turn off the power at the circuit breaker. The switch you are replacing may be labeled, indicating which breaker powers the circuit. If not labeled, turn off breakers individually until the switch no longer has power. Verify it is off using a voltage tester.

It is extremely important to cut power to avoid getting shocked while wiring the 3-way switch. Make sure everyone in your home knows not to turn the breaker back on. Tape over the breaker switch as a precaution.

Removing the Old Switch

To start wiring your new 3-way switch, remove the existing switch:

Unscrew and remove the switch plate cover.
Carefully pull the switch away from the wall enough to view the screw terminals. Do not touch any bare wires yet.
Photograph how the wires are connected, especially if they do not follow typical wiring colors. This will help when reconnecting them later.
Disconnect the wires from the screw terminals. Tape the ends to label hot and traveler wires.
Unscrew the switch and remove it from the wall.
Double check that power is still off using a voltage tester. It should not light up.

Installing the New Switch

With the old switch removed, you can now install the new 3-way switch:

Orient the new 3-way switch with the screw terminals facing downward.
Insert the switch into the wall box at the same spot the old switch was mounted.
Do not attach the wires yet. Just let the switch hang there while you prepare the wires.
The common wire is typically the black hot wire. It needs connected to the dark common screw.
The traveler wires are usually red and black from the 3-wire cable. They connect to the brass traveler screws.
The ground wire attaches to the green screw on the 3-way switch.
With all the wires on the proper screw terminals, carefully push into the wall box. Hold wires in place while tightening screws securely.
Install the switch plate cover and turn the power back on at the breaker once complete.

3-Way Switch Wiring Diagram

Use this 3-way switch diagram as a reference while wiring:

As you can see, the traveler wires allow electricity to flow between the switches, connecting the circuit. The common wire brings power to one of the switches.

Tips for Easy Installation

Follow these tips to make wiring a 3-way switch easier:

Label all wires as you disconnect them to avoid mix-ups.
Only work on one wire at a time to keep everything organized.
Fold wires neatly into the box, keeping hot wires separated.
Double check connections match the old switch and diagram.
Be patient, go slow, and be cautious when wiring. Rushing leads to mistakes.
Having a helper handy provides extra hands when holding wires together.

Conclusion

While it may seem intimidating, installing a 3-way switch is actually quite simple. Following basic safety precautions and carefully connecting the common and traveler wires according to the wiring diagram will allow the switch circuit to function properly. Taking your time is key for a smooth installation. In no time, you will enjoy the convenience of controlling lights from multiple locations in the home.