How garage door photo-eye safety sensors work, why your door won't close, and a troubleshooting guide for the most common sensor problems.
Since 1993, every garage door opener in the US is required to have photo-eye safety sensors — two small units near the floor on each side of the door. They shoot an invisible beam across the opening; if anything breaks the beam while the door closes, the opener reverses. It's the most important safety feature on your door, and it's also the most common reason a door won't close.
One sensor is the sender (it has a small LED) and the other is the receiver. When the beam is unbroken, the receiver's LED stays steady and the door closes normally. When something breaks the beam — a kid, a box, a leaf — the receiver's LED blinks and the opener reverses and the lights flash. A blinking opener light usually means a sensor problem.
1. Check that both sensors face each other and haven't been bumped out of alignment — even a small angle breaks the beam. 2. Wipe both lenses clean; cobwebs and dust block the beam. 3. Check that nothing — a trash can, a bike, a leaf — is in the beam path. 4. Confirm the receiver LED is steady, not blinking.
If the LED is off entirely, the sensor may be dead or the wiring corroded — that's a repair call.
If the door only closes when you hold the wall button down, the sensors are almost certainly the problem — holding the button overrides the sensor reversal. Don't use this as a workaround; it means your safety feature isn't working and the door could close on something. Get the sensors repaired.
Alignment, cleaning, and bracket repositioning are quick fixes. If a sensor is cracked, the LED is dead, or the wiring is corroded, replacement is the answer — sensors are inexpensive and universal-ish (match to your opener brand). We carry replacements for LiftMaster, Chamberlain, and Genie on our trucks. Call 970-408-9827.