What the sensors do
Most garage door sensor problems show up the same way: the door starts to close, then stops and goes back up, or it won't close at all from the remote. The two small boxes near the floor on each side of the door are the safety sensors, sometimes called photo eyes. One sends an invisible beam across the doorway and the other receives it. If anything breaks that beam while the door is closing, the opener reverses. If you've looked through this guide and the door still won't close, call me at (619) 930-7869.
Those sensors are there for a reason. Federal safety rules under UL 325 have required residential openers made since 1993 to reverse when something is in the way, and photo eyes are how most openers meet that. They're the part that keeps a door from closing on a child, a pet or a car, so the goal is always to fix them, never to bypass them for good.
What the lights are telling you
On many LiftMaster and Chamberlain openers, the sending sensor has an amber light and the receiving one has a green light. Genie and other brands use different colors, but the idea is the same: a steady light on both means they're lined up.
- Both lights steadyThe sensors can see each other. If the door still won't close, the problem is probably somewhere else, like lock mode or the travel limits.
- One light blinkingThe sensors are out of line or something is partly blocking the beam. This is the most common one.
- One light offThe receiving sensor can't see the beam at all. Usually misalignment or a blocked lens, sometimes a wiring problem.
- Both lights offNo power is reaching the sensors. That points to a loose wire, a damaged wire, or the opener itself.
- The opener light flashes when you try to closeMany openers flash their main light several times to tell you the sensors are the reason the door reversed. On many LiftMaster and Chamberlain units, that's ten flashes.
What you can check just by looking
- 1Clear the doorwayLook for anything near the sensors: a trash can, a rake, a box, tall weeds. Moving your own things out of the beam is fine.
- 2Look at the lensesDust, cobwebs and water spots are enough to block the beam. If a lens looks dirty, tell me when you call and I'll clean it and check the aim.
- 3Look at the alignmentFrom the side, both sensors should point straight at each other at the same height. If one looks bumped or its bracket is bent, don't loosen or bend anything. Call me and I'll check it. Re-aiming a sensor is a quick job for me.
- 4Notice the time of dayLow sun shining straight into the receiving sensor can blind it, which is why some doors only act up in the late afternoon. If that's the pattern, tell me. A small sun shield or moving the sensors usually solves it.
- 5Look at the wiresFrom the floor, look along the thin wires from each sensor for staples pinching the wire or a spot where it's been chewed. Don't pull on them. Tell me what you see.
If you need the door closed right now
On most openers, if you press and hold the wall button, not the remote, the door will close even with the sensors out. Hold it all the way to the floor. If you let go early, it reverses. That override skips the safety feature, so watch the door the whole time and keep people, pets and cars well clear.
That's a stopgap for tonight, not a fix. A door that only closes with the button held is a door without working safety protection, and it should be sorted out soon.
Never bypass the sensors permanently by mounting them high, taping them together or jumping the wires. They're the main thing keeping the door from closing on someone.
When it's time to call
Call if a light keeps blinking with nothing in the beam, if both lights are dark, if the wire is damaged inside a wall or behind the ceiling, or if the door reverses even with steady lights. Sensors, sensor wiring and the opener's logic board are all part of garage door opener repair, and replacing a set of sensors is a quick job.
On older openers, sensor trouble can be the first sign the whole unit is near the end. If yours is well over a decade old, has no battery backup, or keeps having problems, my guide on whether to repair or replace your opener can help you decide. I cover opener repair in North Park and the rest of Central San Diego. North Park is 5–10 minutes from my base in Normal Heights.
Keeping the sensors happy
Sensors get knocked out of line by bikes, bins, kids' toys and cars parked a little too close. If yours stick out where people walk, I can often move them tighter to the track or onto the wall. Keep the area in front of them clear, and call me if a light starts blinking.
Once a month, test the safety reverse. Lay a roll of paper towels flat in the doorway and close the door. It should touch the roll and go back up. If it doesn't, stop using the auto-close and get it checked.