Those two little sensors near the bottom of your garage door tracks are the reason your door refuses to close — and their indicator lights are trying to tell you exactly what is wrong. Here is how to read them.
What the sensors do
The photo-eye sensors shoot an invisible beam across the door opening. Anything that breaks the beam — a bike, a pet, a child — makes the door stop and reverse. Required on all openers since 1993, they are the most important safety feature your door has.
Reading the lights
- Both lights solid (typically one green, one amber/yellow): aligned and healthy. Your closing problem lies elsewhere.
- One light off or flickering: the sensors are misaligned or a wire is damaged — this is the classic reason a door will not close and the opener light flashes.
- Both lights off: no power to the sensors — check the wires at the opener head and look for staple damage or chewed wiring.
The 5-minute fixes
- Wipe the lenses with a soft dry cloth — dust, cobwebs and road salt film are the #1 culprit.
- Check alignment: each sensor sits on a wing-nut bracket that is easily bumped by a bin or broom. Loosen, aim them at each other until the light goes solid, retighten.
- Block the sun: low sun can blind a sensor at certain hours. A small cardboard shade tube fixes it.
- Inspect the wires for nicks, kinks, or loose terminals at the opener.
What the two lights are telling you
The two small units near the floor on each side of the door are the photo-eye safety sensors. One sends an infrared beam, the other receives it. Each has an indicator light. On most openers, a steady light on both means the beam is aligned and clear. A blinking light, or one light off, means the beam is broken or the sensors are out of alignment, and the opener will refuse to close the door from the remote, though it will usually still close if you hold the wall button down. The exact colours vary by brand, so the manual matters, but the pattern is the same: steady is good, blinking is a fault.
The five-minute fix that solves most cases
Look for anything in the beam path: a garbage bin, a bike wheel, a box, a cobweb across the lens. Wipe both lenses with a dry cloth. Check that both sensors are pointing straight at each other and are the same height off the floor; a sensor bracket bumped by a broom or a car tire is the number one cause. Gently bend the bracket until both lights go steady. If a light is off entirely, follow the wire back to the opener and look for a break, a loose terminal, or a staple through the wire.
When it is not the sensors
If both lights are steady and the door still will not close, the sensors are not the problem. The close-force limit may be reading a binding door as an obstruction, the travel limits may be set wrong, or the logic board may be faulty. Never bypass or disconnect the sensors to force the door closed. They are the only thing standing between a closing door and a child, a pet, or a car bumper, and defeating them is the one thing we will not do on a service call.
Still blinking?
If the lights will not go solid — or they are solid and the door still will not close — the fault is usually wiring or the opener logic board, and that is worth a professional look. Pro Entry Garage Doors fixes sensor and opener problems same-day across Burlington and the GTA. Call 416-666-6745 or book online.