Motion detectors read radiant heat in one area. Light switches with outdoor motion sensor light replace the existing switch on the outside of a house. When there is movement in front of the switch, the light comes on. You do not have to install an external motion detector connected to the light.
Set the main breaker box of the house and turn off the circuit breaker that controls the light switch. If in doubt, turn off the main switch. Remove the cover for the outdoor motion sensor light switch by removing the screws. Use the screwdriver to turn the screw counterclockwise. Remove the two screws holding the light switch on the wall. Touch a voltmeter without contact, available in most hardware stores to the plastic covering the cables.
Wrap duct tape around the wires extending out of the wall, looking at which end of the outdoor motion sensor light switch attached. Remove wire nuts and unscrew the cables ends. If no wire nuts, loosen the screws holding the wires to the light switch. Strip a quarter inch plastic motion sensor switch. Wire nuts put around the red and yellow wires as they are only used for three-way switches.