Garage door sensor not working

Every opener installed since 1993 has a pair of photo-eye sensors about six inches off the floor, one each side of the opening. One sends an invisible beam, the other receives it. If anything breaks that beam while the door is closing, the opener reverses. It's the feature that stops a door coming down on a child, a dog or a bumper, and it is deliberately quick to trip.

So when a door refuses to close and the opener light flashes, the opener is not broken. It's doing exactly what it should, on bad information. The job is to work out why the beam is being interrupted or why the eyes can't see each other, and that is what the visit is for.

Five causes account for almost every sensor call in York.

1. Something in the beamA trash can, a bike wheel, a cobweb, a leaf. Anything in the six inches above the floor between the two eyes trips them, and the door will not close until it is gone.
2. A dull lensRoad salt, dust and the film from a car's exhaust dull the lenses, and a dull lens fails in low light first, so the door misbehaves at dusk before it fails in daylight.
3. A bent bracketEach eye sits in a bracket that bends easily. A bumper, a bin or a bike knocks one out of line, and an eye that keeps drifting out of line every few weeks is a bracket that never holds, not an eye that needs setting a fourth time.
4. Sun in the receiverLate afternoon sun straight into the receiving eye blinds it. A door that only misbehaves at one time of day is nearly always this.
5. A damaged wireA staple through the thin sensor wire, a splice that has come apart, or the terminals at the opener working loose. Both eyes dark is usually a wire.

Both LEDs steady, the beam clear, and the door still reverses? Then the opener is reacting to something else. If it reverses just before the floor, the down travel limit is set a fraction too far and the opener thinks the floor is an obstruction. If it reverses part-way and the door feels heavy, the spring has lost tension and the force setting is tripping. The first is a small adjustment on the visit. The second is a spring job, and the opener should stop being used until it's done.

A door that reverses only in cold weather is a variation of the second: the door gets stiff, the force setting trips. A balance check on the visit settles it.

Sensors do fail outright. Water gets into a lens after years of splash from the driveway, a mower clips one, or a board inside gives up. Replacement pairs for Chamberlain, LiftMaster and Genie are standard stock and take twenty minutes to install and align. Brands don't mix: a Genie opener needs Genie eyes, and the current LiftMaster eyes won't talk to a fifteen-year-old LiftMaster. The model label on the motor housing says which, and the technician reads it.

If the wiring is the problem, it's rerun along the wall with proper clips rather than staples. It's a small job, and one that stops the same fault coming back in a year.

And the brackets: sensors are meant to sit at the same height on both sides, four to six inches off the floor. A bracket that has been bent will drift out of line every few weeks no matter how carefully it's set, so when that's the pattern the technician replaces the bracket rather than realigning the eye a fourth time.

Check the beam, the lenses, the alignment and the wiring, in that order, because that's the order the faults come in. Replace the pair if a lens is cloudy or an eye is dead. Then, before leaving, disconnect the opener and lift the door by hand to check its balance, because a door that reverses often turns out to have two problems, and the sensors were only the one you could see. Free estimate throughout York County.

Most sensor calls are short. The ones that aren't are the ones where the door was heavy all along.

Something's wrong with the motor. Usually not. A door that reverses and blinks is a sensor conversation, not a motor problem. Sort the eyes and the opener is fine.

Just bypass the sensors. Don't. A door without working sensors is the door that comes down on something. Call, and the eyes are working the same day.

Sensors can't be replaced separately. They can, and they are, as a matched pair, on the existing opener, in about twenty minutes.

Say where you are in York, get a two-hour slot, and the technician phones on the way. Same routine in Springettsbury, West Manchester and Dallastown.

Free estimate. Throughout York County, including Springettsbury, West Manchester, Spring Garden, Hanover, Red Lion, Shrewsbury, Dover, Dallastown.