A light fixture controlled by a light sensor is a great addition to any backyard. As dusk approaches, the sensor automatically turns the light on, and the light stays on until the sun's rays trigger it off. This type of light fixture makes your home safer at night while allowing you to get the most use out of your yard. But, because the light sensor is exposed to the elements, it may need to be replaced over time. This is a relatively inexpensive and easy repair any do-it-yourselfer can accomplish in less than an hour.
Turn the power off to the circuit that powers the outside light you're going to work on.
Locate the light sensor on the body of the light fixture. It typically looks like a small round lens, similar to that on a camera.
Use a screwdriver to remove any necessary screws. Open the cover on the light fixture, and remove the bulb. If the bulb was recently on, wait until it cools sufficiently to the touch before removing it.
Remove the bolts that secure the fixture to the wall box. If the wiring is self-contained in the fixture, remove the cover plate that's protecting the wiring.
Use a touch-type voltage tester to check the wires for voltage before you disconnect them. Press the button on the tester, and press its tip to each of the wires in the box. If the tester does not light up or make a beeping noise, the circuit is off. If it does make an alert, you try turning off another breaker, and re-test the wires before proceeding.
Disconnect the light sensor's wires from the wall and fixture wires.
Use needle-nose pliers to loosen the old light sensor by unscrewing it or removing its locknut, if it has one. Once loose, you can unscrew the sensor the rest of the way by hand.
Install the new light sensor by screwing it into the threaded hole left by the previous one. Make sure the weatherproofing grommet is in place on the sensor's shaft before you install it.
Take the white wire from the light sensor, and connect it to the other white wires in the wall box and the white wire from the fixture. Secure the connection with a wire connector, and wrap it with electrical tape.
Take the black wire from the light sensor, and connect it to black wire in the wall box. Secure the connection with a wire connector, and wrap it with electrical tape.
Take the red wire from the light sensor, and connect it to the black wire from the fixture. Secure the connection with a wire connector, and wrap it with electrical tape.
Carefully push all of the wires back into the wall box or wiring box. Re-install the light to the wall or re-install the wiring box cover, depending on your fixture.
Replace the light bulb and fixture cover. Turn the power back on. The light should come on for a few seconds, then automatically turn off.
Test the new light sensor by taping electrical tape over the lens of the sensor so that no light gets through to it. After a few seconds, the light should turn on. Remove the tape, and the light will turn off in a few seconds.