Modern garage doors use photo-eye sensors positioned near the floor on both sides of the opening. These sensors project an invisible beam across the door’s path and reverse the door’s direction when something blocks the signal.

Inspect both sensors for dirt, spider webs, or debris covering the lenses. Clean the sensors with a soft cloth and mild soap solution, then dry them completely. Even small amounts of dirt can interfere with the sensor beam and prevent proper closing.

Verify the sensors align properly by checking that their indicator lights glow steadily. Most sensors show a solid green or red light when aligned correctly. If the lights blink or appear dim, adjust the sensor brackets until both units point directly at each other.

Remove any objects from the door’s path, including tools, bicycles, storage containers, or debris that might trigger the sensors. Check for ice, snow, or leaves that accumulate near the door during weather events. Sometimes invisible obstructions like spider webs or hanging objects cause sensor interference without obvious visual clues.

Test the sensor function by waving a broom handle through the beam while the door closes. The door should immediately reverse direction when you break the beam. If the door continues closing despite the obstruction, call a professional immediately because this represents a serious safety hazard.