If your garage door starts down and then pops back up, or won’t move down at all while the opener light blinks, the safety sensors are almost always the reason. This is the most fixable garage door problem there is: most of the time it takes a rag, a level and ten minutes.
Those two small boxes near the bottom of the tracks shine an invisible beam across the doorway. Federal rules have required them (or an equivalent safety edge) on every opener made since 1993. If anything breaks the beam, or the boxes can’t “see” each other, the opener refuses to close the door. That’s the feature working as designed.
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Signs it’s a sensor problem
- The door goes down a little, then reverses to fully open
- The door won’t close from the remote, but closes if you hold the wall button down the whole time
- The opener’s light flashes several times when you try to close it (many models flash 10 times for a sensor fault)
- One sensor light is off, dim or blinking instead of steady
The 10-minute fix: work through these in order
- Clear the doorway. Check nothing is in the beam’s path: a trash can, a broom, boxes, leaves, even a cobweb across the lens.
- Clean both lenses. Wipe each sensor with a soft, dry cloth. Dust, pollen and spider webs are the most common culprits.
- Check the sensor lights. Most systems have one light on each sensor. The sending side usually glows steadily; the receiving side glows steadily only when it can see the beam. Off, dim or blinking means the sensors aren’t lined up or aren’t getting power.
- Line them up. Loosen the wing nut on the sensor with the blinking light and gently swivel it until the light turns solid, then tighten. A small torpedo level helps get both sensors pointing straight at each other at the same height. Manufacturers typically mount them no more than about 6 inches above the floor.
- Watch for sun glare. Low morning or evening sun shining straight into the receiving sensor can blind it. If the door only misbehaves at certain times of day, that’s the giveaway. Swapping the two sensors to opposite sides or fitting a small sun shield usually fixes it.
- Check the wires. Follow the thin wires from each sensor up to the opener. Look for a staple driven through the wire, a chewed section, or a loose connection at the back of the opener. Unplug the opener before touching any connections.
- Reset the opener. Unplug it for 30 seconds and plug it back in.
If the door still won’t close
If the sensors show steady lights and the door still reverses, the opener may be sensing too much resistance instead. Possible causes:
- Close limit set wrong: the door hits the floor before the opener thinks it should, so it reverses. Adjusting travel limits is covered in your opener’s manual.
- Sticking rollers or a bent track making the door bind on the way down. See garage door off track.
- A failing spring making the door heavier than the opener expects. See broken garage door spring.
- A faulty sensor or logic board that needs replacing
Sensor replacement kits are inexpensive and usually a manageable DIY job if you’re comfortable with low-voltage wiring. Spring, track and roller problems are a job for a technician.
Never bypass the sensors
It’s tempting to tape the sensors together or mount them up high to stop the hassle. Don’t. The CPSC has linked dozens of child deaths to garage doors without working reversing features, which is exactly why the sensors became mandatory. Once a month, test the auto-reverse: place a roll of paper towels or a 2×4 flat in the door’s path. The door should reverse as soon as it touches it. For more ways to keep the garage safe, see our garage door security guide.
What it costs if you need help
| Job | Typical cost |
|---|---|
| Sensor repair, realignment or replacement | $100 – $250 |
| Opener repair (board, limit adjustment) | $100 – $350 |
| Roller replacement | $100 – $250 |
| Service call or trip fee | $50 – $150 |
See every repair price in our garage door price estimator. If the opener is old enough that it doesn’t have sensors at all, it’s time for a new one: openers made before 1993 don’t meet today’s safety standard. Our garage door openers guide explains the options.
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Frequently asked questions
Why does my garage door close when I hold the wall button but not with the remote?
Holding the wall button overrides the sensors on many openers. It’s a sign the sensors are blocked or misaligned. If the remote itself seems dead, see remote not working.
Why is one garage door sensor blinking?
Usually the sensors aren’t lined up, the lens is dirty, or a wire is damaged.
Can sunlight affect garage door sensors?
Yes. Direct low sun into the receiving sensor can stop the door closing at certain times of day.
How high should garage door sensors be?
Most manufacturers specify roughly 4 to 6 inches above the floor. Check your opener’s manual.
Can I replace garage door sensors myself?
Often yes, using the kit made for your opener brand. If you’re not comfortable with wiring, a technician can do it in under an hour.