If The door starts to close, then reverses and the opener light blinks.
Then Photo-eye alignment.
The sensors near the floor are out of line or dirty; a clean and re-aim usually restores normal closing.
Springs
Two springs on one shaft usually age together. When one breaks the other is not far behind, which is why we talk about replacing both at the same time and setting them to the door's actual weight.
Garage Door Roller ReplacementEvery morning the door announces itself: a rattle on the way up, a grinding squeal on the way down, loud enough that the…
Garage Door Hinge ReplacementEvery time the door goes up there is a sharp pop from the same spot, about a metre off the floor, and the whole door gives a…
Garage Door Track Repair or ReplacementAfter a decade of slushy winters the bottom foot of the track is flaking rust.
Garage Door Cable ReplacementThe cable has wrapped itself around the shaft above the door instead of sitting on its drum.
Torsion Spring ReplacementThe door drops the last stretch to the floor rather than settling, and when you stop it halfway by hand it slides down instead of…
Extension Spring ReplacementThe home inspector's report on the house you are buying flags the garage door: extension springs with no safety cable running…
Garage Door Balance AdjustmentReleased from the opener, the door will not hold anywhere.
Which fix fits?
Tap a situation. The answer opens here.
If The door touches the floor and pops back open.
Then Close-limit adjustment.
The opener thinks it hit something; setting the travel limit correctly stops the bounce.
If The door closes but leaves a gap along the bottom.
Then Bottom seal and limit setting.
A compressed seal or a short travel limit leaves daylight; both are simple to correct. Garage Door Bottom Seal Replacement