Install a Motion Sensor

A motion sensor detector.
  • 1 hours
  • Intermediate
  • 100
What You'll Need
Wire Strippers
Needlenose Pliers
Screwdriver (Phillips and Flat Head)
Voltage Tester
Electrical Tape
Wire Nuts
Silicone Sealant

One of the easiest things you can do to help protect your property is to install a motion sensor. It works by turning on when an object or person gets close enough. Let's face it, light is not an intruder's best friend. You will have the added benefit of them lighting your way when you come home at night.

Below you will find two different installation techniques. The first is installing a new light fixture that comes pre-wired with a motion sensor. The second is adding a motion sensor to an existing light fixture.

Before you dive in, please check out this article on a few things to know about motion sensors.

Installing a New Light Fixture With a Pre-Wired Motion Sensor.

Step 1 — Cut the Power

Turn off the power to the circuit you will be working on. Place a strip of the electrical tape over the breaker that controls the circuit. You can also tape a sign to the door of the electrical panel box stating "Keep Out - Working on Electric!"

Step 2 — Remove the Old Fixture

Remove the bulbs from the existing fixture. Use the screwdriver to remove the screws holding the fixture to the box. As you remove the second bolt, make sure to hold onto the fixture so it doesn't fall off. With the fixture hanging by the wires, use your voltage tester to ensure that the power is still off.

With one hand holding the fixture, use your other hand to unscrew the wire nuts and separate the wires. There should be one black, one white, and one green wire. Remove the old fixture.

Step 3 — Install the New Fixture

Light fixtures with pre-wired motion sensors are installed just like a regular fixture. If your new fixture requires a mounting bracket, it will come packaged with one and instructions on how to install it. It may also come with a soft waterproof gasket. Install it as per the instructions as well.

Step 4 — Wiring

Use the needlenose pliers to cut away the weathered part of the exposed wire ends in the box. Use the wire strippers to strip away about 3/8" of insulation from the wires in the box. On most wire strippers there is a guide on the side that shows how much insulation should be stripped.

Line up the black fixture wire and the black box wire and twist them together using the needlenose pliers. Place a wire nut over them and screw it on until tight. Do the same thing with the white wires, and then, connect the green ground wire to the box. Cut a 3" piece of electrical tape and tightly wrap it around the wire nut where it meets the wires.

Gently push the wires back into the box. Attach the fixture to the box with the bolts supplied. It may be easier to start tightening the bolts by hand so you can line the holes up and then use the screwdriver to tighten everything down.

Step 5 — Test it Out

Install new light bulbs and turn the power back on. The lights should automatically come on and stay on for a few minutes. After the lights go out, set the sensitivity of the sensor using the dial on the side or the back of it. There will also be a switch to pick the length of time you want the light to stay on.

Now it's time to clean up and enjoy your new motion sensor.

Adding a Motion Sensor to an Existing Light Fixture

Many exterior light fixtures come with "knockouts" to make installing motion sensors or photocells easier. These instructions are for a fixture with a "knockout." Follow the first and second steps from above. They are the same here.

Step 1 — Locate the "Knockout"

With the fixture removed, you will see a "knockout" somewhere on the plate or the face of it. It will be round and it may have a slit through it so you can unscrew it with a screwdriver.

Step 2 — Install the Sensor

Pick up the motion sensor. It should come packaged with a rubber ring gasket. Fit the wires through the gasket and move the gasket over the threads so that it's right up against the base of the sensor. Guide the wires through the "knockout" hole on the fixture. With the wires through the hole, you should be able to screw the motion sensor into the knockout.

On the inside of the fixture, use the silicone sealant to seal around the knockout where the sensor is located. This will help keep water out.

Step 3 — Wiring

There should be a black, white, and red wire coming from the sensor. The white wire gets connected to the white wire of the fixture and the white wire of the wall box. (See the wiring step above for instructions on connecting wires.) The black wire gets connected to the black wire of the wall box. The red wire gets connected to the black wire of the fixture.

Step 4 — Finish the Job

Gently push the wires back into the box. Connect the fixture to the box with the bolts supplied. It may be easier to start tightening the bolts by hand so you can line the holes up and then use the screwdriver to tighten everything down. Now, follow the last step from above.

Whether you're adding a motion sensor switch to an existing fixture or replacing an exterior light with motion-sensing capabilities, one thing is certain; a simple half-hour job can add a sense of safety to your home that's priceless.

Dave Donovan is a freelance copywriter living in Atco, N.J. An electrician for 15 years, an injury forced him to pursue his true passion - writing.