Why the reversing system matters

An automatic opener drives a heavy door down with real force. Since the early 1990s, residential openers sold in the United States have had to include safety reversal features under the UL 325 standard.

There are two parts to it. The first is contact reversal, where the opener senses resistance and reverses. The second is the photo-eye system, a pair of small sensors near the floor that send an invisible beam across the opening.

Both can drift out of adjustment or fail with age. Sensors get bumped, wiring gets pinched, and force settings get turned up to cover a door that is not running smoothly. Testing is the only way to know they still work.

A door that closes on a car roof or a bicycle is expensive. A door that closes on a child is far worse. The reversing system is the main thing standing between those outcomes, and it costs nothing to check.

How to test garage door auto reverse with a board

This is the contact reversal test. Clear the area first and keep children and pets well away.

  • Open the door fully with the opener.
  • Lay a 2x4 flat on the floor in the center of the door's path.
  • Press the button to close the door and stand clear.
  • Watch what happens when the bottom of the door touches the board.

A passing door stops as soon as it meets the board and travels back up. A failing door stops and stays down on the board, or keeps pressing on it. Either way, do not keep using the opener until it is checked.

Why a 2x4 laid flat? It gives the door a low, solid obstacle about an inch and a half high. That is close to the height of a small object or a child's foot. If the opener cannot sense it, it will not sense a person either.

Run the test from the fully open position, not from partway. You want the door moving at its normal closing speed when it meets the board.

What the force standard asks for

UL 325 expects a residential opener to reverse when it meets a modest amount of resistance, roughly 20 pounds. That is far less than the door could push with if it were allowed to.

Some testers check this by holding up the bottom of the closing door with their hands. That is not a test for a homeowner to do. The board test above gives you the same answer without putting your hands under a moving door.

If the door only reverses when it hits something solid and heavy, the force setting may be too high. That is worth having looked at.

Force settings are usually two small dials or buttons on the motor head, one for opening and one for closing. Older openers often have screws. Turning them up makes the door push harder before it reverses. That can hide a binding door, and it makes the door more dangerous.

The photo-eye sensor test

The second check confirms the beam does its job. Start closing the door, then pass an object such as a broom handle or a cardboard box through the beam between the two sensors.

Use an object, never your body or your foot. If the door reverses and opens, the sensors are working. If it keeps coming down, stop it with the wall button and stop using the opener.

While you are there, look at the sensors themselves. Both lights should be steady. A blinking light often means the two eyes are out of line, dirty, or getting too much direct sun.

The sensors should sit a few inches above the floor, generally no more than about six inches up, facing each other across the opening. If one is mounted high, a small child could pass under the beam without the door noticing.

Wipe the lenses with a soft cloth if they look dusty. Check that nothing, such as a trash can or a garden hose, sits in the beam path. Spider webs across the lens are a surprisingly common cause of a door that refuses to close.

What to do if your door fails

Many openers have close-force or sensitivity adjustments, described in the owner's manual. A small correction sometimes fixes a borderline result. If you adjust it, run both tests again right after.

If the door still fails, or if it only passes when the force is turned up, the real problem is often the door. Worn springs, binding rollers or a door out of balance make the opener work harder, and turning up the force hides that. Do not touch springs or cables yourself. Those parts hold stored tension.

The U.S. Consumer Product Safety Commission recommends testing the reversing mechanism once a month. If you would rather have a trained eye on it, Johnny Garage Door Service offers a garage door safety inspection. The company is open 24/7, has been in business since 2004 and offers a 90-day parts and labor warranty.

Monthly testing sounds like a lot, but it is quick. Pick an easy reminder, like the first weekend of the month, and run both tests back to back. Write down anything odd, such as a door that reverses slower than it used to.

Remember that the door itself should also be in good shape. A door that sticks, shakes or makes grinding sounds is giving you a warning. Have it looked at before the opener tries to muscle through it.