Photocell light contols use a photocell to determine when to turn a light on and off. These control units are used on street lights, residential security lights and now automobile lights. Small control units may have two terminals, which are connected to a circuit like a regular switch. Larger control units have three terminals, which are actually two circuits sharing a common hot wire. One circuit houses the photocell, and the other circuit holds the switch that the photocell activates to turn on the lights.
Shut off the power to the circuit or power source that will provide power for the light.
Look at the light control unit and review the manufacturer's installation instructions. Locate the hot wire common terminal on the control unit. This terminal should connect to the black hot wire of the power source.
Connect the white wire of the power source to the white wire of the control unit. Connect the red wire of the control unit to one of the two terminals of the light. Connect the second terminal of the light back to the black hot wire of the power source.
Turn the power source back on and cover the photocell on the light control. The light should turn on in a few seconds. Uncover the photocell and the light should turn off. This test should be done in bright daylight.