How to Test Your Garage Door Safety Sensors and Auto-Reverse

Your garage door opener has two safety systems that keep a closing door from trapping a person, a pet or a car. Both can drift out of adjustment without any warning, so the only way to know they work is to test them.

The tests are simple and take about five minutes. Many opener manuals recommend doing them once a month. Here is how.

The two systems, in plain terms

Photo eye sensors. These are the two small units mounted on either side of the door, a few inches off the floor. One sends an invisible beam and the other receives it. If something breaks the beam while the door is closing, the opener should stop and reverse the door.

Contact auto-reverse. This is built into the opener itself. If the closing door meets resistance, like an object on the floor, the opener should sense it and send the door back up. The photo eyes see things in the way. The auto-reverse feels them.

Test 1: the photo eyes

1. Make sure the door's path is clear and everyone is out of the way.
2. Press the button to close the door.
3. While the door is coming down, pass an object through the beam between the two sensors. A broom handle or a cardboard box works well. Never use your hand, foot or body.
4. The door should stop and reverse back up.

If the door keeps closing, the sensors aren't doing their job. Until it's fixed, don't count on the opener to stop for anything in the way. If you have to close the door, stand where you can see the whole doorway, keep people, pets and cars clear, and have it checked soon. Read on for what to check.

Test 2: the auto-reverse

1. Open the door fully.
2. Lay a piece of 2x4 lumber flat on the floor in the middle of the doorway, under the door. Lying flat, it stands about an inch and a half tall.
3. Close the door with the remote or wall button.
4. When the door touches the board, it should stop and reverse within a moment or two.
5. Remove the board once the test is done.

If the door presses down on the board and stays there, or strains against it, the auto-reverse isn't working correctly. That usually means the opener's force or travel settings need adjustment, or the door itself is binding.

If the photo eye test fails

Start with the easy things. Most sensor problems are one of these:

• Dirty lenses. Wipe both lenses gently with a soft cloth. Dust and cobwebs are common culprits.
• Misalignment. A bumped sensor can point slightly off. Most sensors have an indicator light, and many use a steady light when aligned and a blinking or dark light when they aren't. Your manual will say what the lights mean for your model.
• Something in the way. Look for a trash bin, a hose or a leaf pile blocking the beam.
• Wiring. Look for a loose, chewed or pinched wire running from the sensors up to the opener.
• Bright sunlight. Strong direct sun hitting a sensor at certain times of day can interfere with it.

If cleaning and a gentle realignment don't fix it, have it checked.

If the auto-reverse test fails

This one is less of a do-it-yourself job. The fix usually involves the opener's force and travel settings, and getting those wrong can make things less safe. Turning the force up to make a door close is a common mistake, since it makes the opener push harder against anything in its path.

A door that binds in the track, has worn rollers or is out of balance can also throw off the auto-reverse. Those problems involve parts under tension or parts that affect balance, so it's a job for a professional. Until it's fixed, don't count on the opener to stop for anything in the way. If you have to close the door, stand where you can see the whole doorway, keep people, pets and cars clear, and have it checked soon.

Things to never do

• Never tape the sensors together, mount them up high or otherwise bypass them.
• Never test with a person, a child or a pet.
• Never let kids play with the remote or run under a closing door.
• If your opener has no sensors near the floor at all, it is likely old enough to predate current safety requirements. It's worth replacing. See repair or replace your opener.

For more household safety habits, read garage door safety every family should know. If your door is reversing when nothing is in the way, see why your garage door starts to close, then reverses.