Outside lights that turn on automatically when the sun goes down and turn off when the sun comes up are one of the modern world’s handy conveniences and a great home security feature.  But what if these lights are no longer working properly? What if after replacing the bulb, these lights don’t come on at night? Or what if they never turn off? It may be time to replace the photo sensor switch.

About Photo Sensor Switches
Some outside lights are equipped with this automatic switch so you don’t have to remember to turn the lights on at night and turn them off in the day. This photo sensor switch is activated on and off by sensing light level around it. At night, in low light levels, the switch is activated and the lights comes on. When the sun comes up, high light levels deactivate the switch and turn the lights off. Simple. Pictured are a couple of examples of photo sensors. One stayed on all the time (possibly because the plastic over the sensor had gotten old and discolored), the other no longer turned on (not to built to last forever). How do you know the sensor is the problem?

Trouble shooting
If after replacing an outside light bulb that was not coming on, and it is still not working, it is a safe bet that your photo switch has failed. If you want to be sure, you can place a piece of black electrical tape over the sensor’s eye and test the voltage coming out of the sensor going to the light. If you have no voltage coming out of the switch, but you do have voltage coming into the switch….the switch is faulty. Sometimes the lights are on all day and night and once again, it is a safe bet that the photo switch is faulty. In this case, the switch won’t turn off. No need to do further testing. The switch is faulty. Fortunately, this is an easy fix.

Replacing the switch
Photo switches are not expensive ($10-$15) found at any hardware store or Home Depot nor are they difficult to replace if you have a basic understanding of electrical wiring. Your photo switch will have three wires, black(hot), white(neutral) and red (energized line to your light). After turning off the breaker to the photo switch, simply replace it with your new switch making sure you wire it correctly. Black from your panel to Black, White to White and Red to Black going to your switch. Just remember that the red wire ties into the black line going to your light.
After you turn you power back on if it is night the switch should turn you light on immediately. If it is daytime, then to test, place a piece of black electrical tape over the sensor eye and your lights should come on in a few seconds to let you know that everything is working correctly.

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