Photo-eye sensors are the most-blamed and least-understood part of a garage door system.
The green LED test
Both sensors should show a solid green LED when aligned. If one is blinking or off, that's your problem.
Common causes
Bumped brackets, spider webs, condensation inside the lens, sunlight in the beam path at certain times of day.
The fix
Wipe the lenses, straighten the brackets so both LEDs go solid, test the door.
