Outdoor motion sensor lights are useful for numerous purposes. They make your home more welcoming to nighttime visitors, deter nocturnal animals and are helpful as a security device to light up dark areas of your property. They are a useful accent to your home, unless they do not work the way they should.
Ensure that a wall switch inside the house does not control the light. If there is, make sure the light switch is in the "on" position.
Change out the light bulbs. It is possible for more than one light bulb to burn out at the same time, especially if a storm caused an electrical surge. Try fresh bulbs in each light socket.
Confirm that power is reaching the motion sensor. Remove a bulb and touch the non-contact voltage tester to the light socket. If there is no power, check your electrical switch box to see if the breaker has tripped. Looking at your box, this should be obvious as the breaker switch will be in the "off" position. If the breaker is on but no power is reaching the motion sensor light socket, the light fixture itself may be wired incorrectly or need to be replaced.
Verify that nothing is blocking the motion sensor itself such as plants or garden accents. Clear all plants away from the motion sensor. If the motion sensor cannot receive input, it will not turn the light on.
Review the instruction manual for the motion sensor light to see if it has a light sensor allowing it to turn on when it detects low light levels. If so, there may be a street light or reflection tricking the sensor into thinking it is not yet dusk. If this is the case, use a piece of aluminium foil to shield the sensor from the artificial light.
Ask your neighbours if there was a recent power outage. Motion lights have a time delay after being triggered that will keep them on for a length of time. Accidentally powering off the lights during this time delay will keep them locked on. Wait until after dark and trigger the motion sensor by moving your hand in front of it. After the time delay, the lights will return to normal cycling of off and on.
Watch for nocturnal insects constantly triggering the motion sensor. Large June bugs or moths can trigger the motion sensor, drawing even more insects to the light. This steady insect activity will continually trigger the motion detector keeping the lights on. Cool colours in the blue and white range attract bugs. Replacing the light with a yellow light bulb or with a bulb advertised not to attract bugs will help this problem. If your lights and motion sensor are separate devices, move the sensor away from the light and to another area. Bugs attracted to the light will not continually trigger the motion sensor.
Search for an "always on" switch option on the light. Many motion sensor models have an option to switch between motion sensing and always on. This option is useful if you are having a garden party and do not want the light to keep turning off and on. Check your user manual for this feature and for the location of the switch. Moving it back to the motion sensing position will allow the light to turn off.
If you suspect electrical problems with the wall receptacle itself, call in a professional. Electricity is dangerous to work with unless you are experienced.