Garage door won't close? Check the safety sensors
A garage door that starts down and then reverses, or won't close while the opener light blinks, usually has a problem with the safety sensors near the floor. They may be dirty, bumped out of line, or blocked. Cleaning and realigning them is a free fix, and it's worth getting right, because those sensors keep the door from closing on people and pets. Bright sunlight hitting a sensor straight on can also confuse it, which is why some doors misbehave only at certain times of day.
How the safety sensors work
Most openers have two small sensors, one on each side of the door opening, a few inches off the floor. One sends an invisible beam to the other, and if the beam is broken, the opener won't close the door, or it reverses.
Each sensor has an indicator light. Usually one stays lit to show it's sending, and the other stays lit when it sees the beam; a blinking or dark light points to misalignment or a wiring problem. Your opener's manual shows what its lights mean.
Why the door won't close
Even a small object stops the door.
A bump knocks one off its aim.
Dust or bright sun interferes with the beam.
A loose, stapled or chewed wire to a sensor.
| What you see | Likely cause | What to check |
|---|---|---|
| Starts down, then reverses | The beam is broken | Clear the path; clean and align the sensors. |
| Opener light blinks, won't close | Sensors not seeing each other | Check the sensor lights and alignment. |
| A sensor light is off | No power to the sensor | Check its wires. |
| Door is heavy or crooked | A spring or cable problem | Call a garage door pro. |
Clean and realign the sensors
- Clear the pathLook for anything in the doorway or near the sensors: a bin, a broom, leaves, a spiderweb. Even a small object breaking the beam stops the door.
- Clean the lensesWipe both sensor lenses with a soft cloth. Dust, cobwebs and water spots can block the beam, and bright sun shining straight into a sensor can interfere with it.
- Check the lightsLook at the indicator lights on both sensors and compare them with the manual. A blinking or dark light on the receiving sensor usually means the beam isn't reaching it.
- Realign the sensorsLoosen the sensor's mounting nut or screw, aim it straight at the other sensor, and tighten it once its light stays steady. A level or a string line between them helps get both at the same height and pointing straight.
- Test itClose the door with the remote. Then test the safety reverse the way your opener's manual describes; the door should reverse when the beam is broken or it meets an obstruction.
Watch it done
- Both sensor lights stay steady
- The door closes all the way with the remote
- The door reverses when the beam is broken or it meets an obstruction
If it still reverses
If light or water gets in under the closed door, see the guide for replacing a garage door bottom seal.
If one sensor's light won't come on at all, check its wires for damage or loose connections at the sensor and at the opener. A staple through a wire or a chewed cable is a common cause.
If the door reverses even with both sensor lights steady, the door may be binding or the travel limits may be off. If it also squeaks or grinds as it moves, tighten and lubricate the door. Don't turn up the force setting to make it close; a garage door technician can check the balance, springs and opener settings.
What a pro typically charges (a rough estimate; prices vary by area): A garage door technician typically charges $100–$250 for a service call; spring replacement usually costs $150–$400.
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