How to Wire a Three-Way Light Switch Outside

Introduction

Wiring a three-way light switch outside allows you to control an outdoor light from two locations. This can be very convenient for controlling porch lights, security lights, and landscape lighting. While it may seem complicated, wiring a three-way switch is not too difficult if you follow some basic steps. In this guide, I will walk you through the entire process of wiring a three-way light switch for an outdoor light.

Things You Will Need

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

• Two 3-way light switches - You will need a pair of compatible 3-way switches. These have three terminals - common, traveler, and ground.

• Electrical box for each switch - You will need a box to house each 3-way switch. Outdoor boxes are available.

• NM cable - Also called Romex. This is the standard 2 or 3 wire cable used for indoor residential wiring. You will need two lengths.

• Wire connectors - To join the wires together.

• Wire strippers - To strip the NM cable wires.

• Voltage tester - To make sure the power is off before wiring.

• Screwdrivers - For securing switches and connecting wires.

Step 1: Turn Off Power

The first step is to turn off power to the circuit you are working on. Locate the breaker powering the outdoor light and turn it to the OFF position. Verify power is off by using a voltage tester on the wires. Working with live electricity can result in shock or death.

With the power OFF, you can now safely work on installing the new switches and wiring.

Step 2: Install Switch Boxes

Next, you will need to install switch boxes to house each 3-way switch. For outdoor installation, be sure to use exterior-rated boxes listed for wet locations. Mount the boxes at the desired switch locations following manufacturer instructions. Having the boxes in place will make wiring much easier.

Tip: The two switches can be placed up to 250 feet apart from each other. Consider accessibility and convenience when locating them.

Step 3: Run the NM Cable Between Boxes

Now it's time to connect the two switch boxes together with NM cable. You will need to run a length of cable between the two box locations. Keep the following in mind:

• Use 12/2 or 12/3 cable for 15 ampcircuits. 14/2 or 14/3 can be used for 15 amp circuits if run is less than 100 feet.

• The cable must be protected if run through areas at risk of damage. Conduit or other shielding can be used.

• Outdoors, be sure to use exterior-rated NM-B W/G cable.

• Only make connections with the power OFF for safety.

Leave plenty of extra wire at each box so you have room to work. With the cable connected between boxes, you are ready to move on to connections.

Step 4: Connect the Common Wires

At this stage, you will connect the common wires between the two switches and the light fixture. These will be attached to the common terminal on each switch.

• At the fixture box, connect the common wire from the NM cable to the common wire leading to the light. Use a wire connector to join them.

• At each switch box, connect the common wire from the NM cable to the common terminal on the 3-way switch. The common terminal is usually darker.

The common wire now runs between the light and both switches so they can control the circuit.

Step 5: Connect the Traveler Wires

Next you will connect the traveler wires. These wires allow the switches to communicate and synchronize.

• In the NM cable, there will be two traveler wires of the same color. Typically red or black. Mark one of them with tape so you can tell them apart.

• At each switch box, connect one traveler to the traveler terminal on the 3-way switch. Be consistent with the marked wire.

• Do not connect the travelers to the light or to ground. Only between traveler terminals.

With the travelers connected correctly, your 3-way circuit should now function properly.

Step 6: Connect the Ground Wires and Install Switches

Finally, finish up by connecting ground wires and mounting the switches:

• Connect the bare or green ground wires together in each box using a wire connector.

• Secure the 3-way switches in their boxes following manufacturer instructions.

• Verify ground connections are tight and mount the switch boxes securely.

Once completed, turn the breaker back ON to restore power. Then test that the switches operate the light properly. Enjoy your new outdoor 3-way lighting!

Troubleshooting Tips

If the 3-way switch circuit does not work, here are some troubleshooting tips:

• Use a voltage tester to confirm power to the common wire, but not the travelers.

• Check that the traveler wires are consistently connected. Swapping them can cause issues.

• Verify the common wire is connected properly between the light and both switches.

• Check ground connections and make sure neutral wires are isolated.

• Inspect all wiring for errors in connections or damaged cables.

• Test the switches by switching their position and watching for light operation.

Thoroughly checking connections and wires is usually enough to find any wiring errors. However, if problems persist, contact a licensed electrician for assistance.

Conclusion

Installing a 3-way switch for outdoor lights takes planning and care. But with good preparation and by following key wiring steps, it can be a straightforward DIY project. The ability to control lights from multiple locations is very handy for security, convenience, and creating your desired ambiance outside your home.