Safety Sensors and Auto-Reverse, Explained
Modern openers have two safety systems meant to keep a closing door from trapping a person, pet or car. They only protect anyone if they are aligned, adjusted and tested. Here is how they work and how to check them.
Two systems, one goal
Photo-eye sensors sit a few inches above the floor on each side of the opening and shine an invisible beam across it. If something breaks the beam while the door is closing, the opener reverses. Contact reversal is built into the opener: if the door meets resistance on the way down, it stops and goes back up. Openers sold in the U.S. since the early 1990s are required to have entrapment protection.
The monthly test
The U.S. Consumer Product Safety Commission recommends testing the reversing feature regularly (U.S. Consumer Product Safety Commission, garage doors and openers):
- Lay a piece of wood or a roll of paper towels flat on the floor under the door.
- Close the door with the opener. It should reverse when it touches the object.
- Open the door, then wave something through the photo-eye beam while it closes. It should reverse.
If either test fails, stop using the opener's close function until it is adjusted or repaired.
Why a door reverses on its own
- A sensor got bumped by a bike, a trash cart or a shovel and is out of line. Most have a light that blinks or goes out when misaligned.
- Dirt, cobwebs or low winter sun hitting a lens.
- A loose or damaged sensor wire.
- Close force set too sensitive, or a door that binds partway down.
Kids, pets and the door
- Mount the wall button high enough that small children cannot reach it.
- Keep remotes out of play areas.
- Teach children never to run under a closing door.
- Keep the area under the door clear of toys and bins.
Older openers
An opener with no photo-eyes, or one whose reverse cannot be adjusted to pass the test, is worth replacing. Product recalls are listed by the CPSC (U.S. Consumer Product Safety Commission). See opener repair and installation.
Related pages: garage door opener repair & installation, garage door repair, new garage door installation, and what shapes an estimate.
Sources: U.S. Consumer Product Safety Commission, garage doors and openers; U.S. Consumer Product Safety Commission.
Short answers
How high should the sensors be?
Near the floor, typically no more than about six inches up, so they can detect a small child or pet.
Why does my door only close if I hold the wall button?
Many openers allow a held-button close when the sensors are blocked or misaligned. It is a sign the sensors need attention.
Can sunlight affect the sensors?
Yes. Low sun shining straight into a lens can interfere. Shading or swapping the sensor sides can help.
How often should I test auto-reverse?
The CPSC recommends monthly.
Related garage door work
Garage Door Opener Repair & Installation
Repair or replacement for openers that hum, click, reverse, run slowly or ignore the remote, with chain, belt and wall-mount options and sensor checks.
Garage Door Repair
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New Garage Door Installation
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