The door goes up without complaint. You press the button, it starts down, and then it either stops dead or runs a foot and climbs straight back to the top. Most of the time that is the door protecting itself rather than the door breaking, and the order you check things in saves you money. Four of the causes below cost next to nothing to put right. The fifth means you stop using the door today, and here on the coast one of them is not a fault at all.
Begin at the two photo eyes
Both eyes bolt low on the vertical tracks, roughly a hand span above the slab, and they have to see each other in a straight line before the opener will allow any downward travel. Each should show a steady indicator. A blink, a flicker or a dead lamp means the beam is broken or the pair has drifted out of line. Take hold of one bracket and see whether it moves under your fingers. Bracket feet corrode at slab level where hose water and salt collect, and a softened bracket lets the eye tilt a couple of degrees, which is all it takes. Wipe both lenses with a dry cloth. A haze of salt mist and a spider web behind the housing read to the opener exactly like a child standing in the opening.
Late afternoon sun off the Pacific can blind a west facing eye
This one catches people out and there is nothing broken to find. In the last hours of daylight the sun sits low over the water and comes in almost horizontally under the door. The receiving eye cannot pick its partner out of that glare, so it reports the beam as blocked and the opener refuses to close. The giveaway is timing. If the door shuts perfectly at eight in the morning and argues from four until dark, the hardware is fine. Rotating the pair so the receiver faces away from the opening, or fitting a small hood over the lens, deals with it. Garages on the numbered streets off The Strand and along Coast Highway see it most, because the driveway looks straight out at the horizon.
Obstructions, and the ridge of sand nobody looks for
Kneel down with a torch and look along the bottom of both channels. Bin lids, a bike pedal, a coiled hose and a dropped socket all stop a door the same way. Then look for the local one. Fine windblown sand builds up in the lowest two feet of each vertical track and packs in behind the bottom roller, so the wheel rides up over the ridge instead of running through it. The door shudders, the opener reads that as resistance and reverses. Brush the channel out dry with a stiff hand brush and vacuum what falls. Resist the urge to spray anything in there. Grease inside a track collects the next fortnight of sand and turns it into grinding paste, which is worse than the sand was.
The two opener settings that drift
Down travel and force sit on the motor head and both wander over the years. Travel tells the opener where the floor is, and set a fraction too far the door presses its seal into the slab, the motor feels a collision and back up it goes. Force decides how much resistance counts as hitting something. A bottom seal hardened by the sun produces the same complaint with neither setting having moved, because the rubber no longer squashes. Adjust in small steps. After every change, lay a length of timber flat in the opening and confirm the door reverses off it. That reversal has been a federal requirement under UL 325 since 1993 and it is the last thing between the door and whatever is underneath.
The version where you stop pressing the button
Look at the door with it partly open and check whether the top edge runs parallel to the header. A corner hanging an inch or two low, a cable lying slack beside a track, or a coil above the opening with a finger width gap in it all say the same thing: the counterweight or the cable on that side has failed. Pull the emergency release cord, leave the door exactly where it stands, and keep cars and children out of the opening. Cycling the opener to see whether it will manage one more trip is how a spring bill turns into a spring, cable, bracket and opener bill. A wound spring holds its full energy with the door flat on the floor, so it and the bottom brackets stay off limits.
Rough figures so you know what you are hearing
Sensor realignment sits at an estimated $75 to $150. A diagnostic visit is an estimated $39 to $89. Clearing the tracks and resetting travel and force usually falls inside a tune-up at an estimated $89 to $165. Lift cables come in at an estimated $135 to $245 for the pair, and a single torsion spring at an estimated $185 to $340. Those are guide bands rather than quotes, and the licensed local pros we connect you with in Oceanside CA will confirm the number at the door once they can see which fault you actually have.