Photo-Eye Sensor Alignment or Replacement: getting ready

After a cold night the door stays open until the garage warms up. There is frost on the sensor lenses and a ridge of salty slush piled against the brackets where the snow blower was parked.

Worth answering before the call

Does it happen at all hours, or mainly on bright mornings or late afternoons? Are there sensors at the floor on both sides, or are they missing or mounted up beside the motor? How many doors and openers are there?

Could the door's force setting be the real reason it reverses?

Sometimes. The opener also backs up when it meets more resistance than its force setting allows: an iced seal, a limit that drives the door into the slab, rollers stiff with cold. From the driveway that looks identical to a beam problem. Timing is a clue, not proof, since a flickering beam can reverse the door partway and severe binding can trigger a force reversal right at the start; the sensor lights and diagnostic pattern settle which it is. The technician checks both so the right thing is fixed.

Could the wiring be the problem rather than the sensors?

Frequently. The sensors are fed by a thin two-conductor wire from the head unit that crosses the ceiling and drops down both sides of the door, and it is pierced by staples, cut by shelving screws, chewed by mice or pulled from its terminals more often than a sensor fails. Both sensor lights dark, or an opener code for an open or reversed circuit, points to the wire. The technician tests the run with a meter and repairs or replaces the damaged section.