How Garage Door Sensors Work

Safety sensors (photo eyes) sit near the bottom of the garage door on each side, about 15cm from the ground. One sensor sends an infrared beam; the other receives it. When the beam is broken by an object (or misaligned), the door reverses or refuses to close. This is a safety feature — the sensor is working correctly when it prevents closing.

Diagnosing the Problem

  • Door reverses immediately after starting to close: Sensor beam is broken or sensors are misaligned
  • Sensor light blinking or off: Misalignment or wiring issue
  • Both sensor lights solid but door still reverses: Something is blocking the beam
  • Door opens fine but will not close at all: Sending sensor may have failed

Step-by-Step Fix

  1. 1

    Check for obstructions in the sensor path

    Look for any object, debris, cobweb or even a spider between the two sensors. The beam is invisible but anything interrupting it will trigger the safety reversal. Clear the area completely.

  2. 2

    Clean the sensor lenses

    Wipe both sensor lenses with a clean dry cloth. Dust, dirt, spider webs or even moisture on the lens can scatter the beam enough to trigger the safety mechanism. This fixes many cases of unexplained sensor issues.

  3. 3

    Realign the sensors

    Each sensor is mounted on a bracket and can be angled up, down or sideways. Loosen the wing nut or screw holding the sensor. Angle it so both sensors point directly at each other. The indicator lights guide you: the sending sensor (usually amber) should be a solid amber light. The receiving sensor (usually green) should be solid green when aligned correctly. Blinking green means misaligned — adjust until both are solid. Tighten the bracket.

  4. 4

    Check the sensor wiring

    Inspect the wires running from each sensor up to the motor unit. Look for damaged insulation, pinched wires, or loose connections at the motor terminal board. Reconnect any loose wires to the correct terminals (usually white and white/white or white and white/black).

  5. 5

    Test

    Close the garage door using the button. It should close fully without reversing. Wave your hand through the beam while the door is closing — it should immediately reverse. If it does not reverse when the beam is broken, the safety system is not working correctly and should be serviced.

Sun interferenceDirect sunlight shining into the receiving sensor in the morning or afternoon can overwhelm the infrared beam and cause intermittent sensor failures. If the door only fails at certain times of day, sun interference is likely. A cardboard shade taped above the sensor (or repositioning the sensor slightly) usually resolves it.

Frequently Asked Questions

Technically yes — most garage door openers can be forced closed by holding the wall button continuously. However, bypassing safety sensors is dangerous and should only be done temporarily when troubleshooting, not as a permanent workaround. The sensors exist to prevent the door crushing people, pets or vehicles. Fix the sensor issue rather than bypassing it.
Check the close force and travel limits settings on the motor unit — if the door is hitting the floor or resistance and the close force is set too low, it will reverse thinking it hit an obstacle. Adjust the close force (refer to your opener manual). Also check the door itself for mechanical resistance: worn springs, bent tracks or an unbalanced door all create resistance that can trigger the safety reversal independent of the sensors.