Safety sensors: sensors located at the bottom corners of door that keep door from closing when door opening is obstructed and keeping opener from closing door on a car, animal or a person. There are two functions for the LED lights on sensors. Not all sensors have different color lights. The two different colors represent witch sensor is the transmitter and which is the receiver. Also when both lights are lit up with a steady solid light this means both sensors are aligned correctly. When they are not lit up than there is an obstruction or they have been knocked out of alignment.

sensors broke? here are some costs and prices…

If your sensors have broken and need to be replaced then you should always change them both because you can’t always determine which one is bad. You will sometimes find replacement sensors at hardware stores usually only for the more common brands of openers like Liftmaster/Craftsman and Genie/Overhead door. The can cost you 50 to 75 dollars a pair. They are always sold in pairs. You won’t find less common brand opener parts at stores like Marantec or Linear brands. If you have a local garage door company replace them than you could pay 150 to 200 dollars.