A solar light sensor is a device that uses light to activate or deactivate a switch. The most common type of solar light sensor is the photoresistor, which is used in streetlights and solar lights. When the photoresistor is exposed to direct light sources, it decreases resistance and allows current to flow through the circuit,. One way to tell if your solar light sensor is broken is to check the light itself. If the light is not coming on at all, then the sensor is likely not. If your outdoor solar lights have stopped working, it may be because the sensor is not functioning properly. Fortunately, it is relatively easy to fix solar lights. Here are five steps to help you get. When your solar lights stop working, it can be frustrating. But, with a little troubleshooting, you should be able to figure out the problem and get your lights working again in no time. Solar lights are a great way to add light to an area without increasing your energy bill. However, solar lights rely on a sensor to trigger the light to turn.