How to tell if garage door sensors are misaligned?

You can tell if garage door sensors are misaligned by observing LED lights, door behavior, and physical position of sensors that prevent door from closing properly. The sensors, located on each side of garage door near floor, have LED indicators: typically one sensor shows steady amber or yellow light and other shows steady green when aligned and receiving beam. If receiving sensor green light is flashing, blinking, or off, it indicates misalignment or obstruction blocking infrared beam. Another sign is door that will not close when you press wall button or remote, but will open, or door starts to close then immediately reverses and goes back up with opener lights flashing 10 times, which is LiftMaster error code for sensor issue. Physically, sensors may look crooked, pointing away from each other, at different heights, or brackets loose and wobbly from being bumped by foot or shovel. Sunlight hitting receiver can cause intermittent misalignment. To test, try blocking beam with object; if door does not reverse, sensors not working. You can also check for spider webs, dirt, or leaves covering lens that mimic misalignment. To fix, loosen bracket wing nut, adjust sensor until green light steady, then tighten. Keep sensors 4 to 6 inches high and clean lenses. If lights still flash after alignment, check wiring for damage.