The door won't close. Usually, that is a safety feature.

Rule one: nothing may block the beam

Two small sensors face each other across the opening, about six inches off the floor. If anything interrupts their infrared beam while the door is closing, the door reverses. That is the rule that keeps bumpers, bikes, and ankles safe, and it is the cause of most won’t-close calls.

The sensors fail the polite way. A rake handle leaned across the opening, a shop vac hose, a cobweb thick enough to read as an obstruction, or one bracket nudged out of line by a trash can. Each sensor has an indicator light: on most brands, both glow steady when aligned and one blinks when they disagree. Clear the beam path, wipe both lenses, and gently bend the nudged bracket back until the blinking stops.

One Greenfield-specific note: on west-facing garages, the low sun in late afternoon can flood a sensor lens directly and mimic an obstruction. If the door closes fine in the morning and refuses at 6 PM, that is the sun, not a part. A cardboard shade tube over the lens ends it.

Rule two: the floor must be where the door expects it

The opener has a programmed down-limit, its belief about where the floor is. If the limit drifts, the door touches concrete before it expects to, reads the resistance as hitting an obstacle, and reverses back up as if it struck something.

The tell: the door goes all the way down, touches, then immediately climbs back up. Cold makes it worse, because steel tracks contract and the door sits a hair lower in January than it did in July. Limit adjustment is a small screw or a button sequence depending on the unit, and it is genuinely a homeowner-doable fix if you have the manual. Without the manual, it is a ten-minute part of a tune-up visit.

Rule three: the force must stay reasonable

Openers also monitor how hard they are working on the way down. A door with a failing spring, dry rollers, or a bent track section demands more force, and the opener refuses rather than crush whatever might be under it.

This is the case that deserves respect, because the refusal is a symptom of real mechanical trouble. If the door also groans, jerks, or sits crooked in the opening, stop cycling it and look at the spring page or the emergency page if it is stuck open with evening coming.

When it is none of the rules

A door that starts down and stops dead partway, without reversing, has usually met a physical blockage in the track or thrown a cable. Off-track doors hold their position by friction and habit. Keep people out from under it and leave it where it stopped.

Closing the door tonight anyway

If the sensors are the problem and it is dark and cold, most openers will close the door if you hold the wall button down continuously until the door seats. That is the built-in override, and it works exactly once per press, with you standing there watching the whole travel. It gets the house sealed for the night. It is not a fix, and the sensors still need their alignment visit: (317) 526-4415 gets that scheduled anywhere in the county.