Garage door sensor alignment: fixing the blinking light

What the lights are telling you

Every opener made since the early 1990s has two photo-eyes mounted about six inches off the floor, one on each track. One transmits an infrared beam, the other receives it. Break the beam and the door refuses to close.

On most units the transmitter shows one steady colour and the receiver another. Both steady means aligned and working. One blinking means misaligned or obstructed. One dark means no power to that unit — usually a wiring fault. Both dark means the circuit is dead at the opener end.

Aligning them

Unplug the opener first. Loosen the wing nut or bracket screw on the blinking sensor just enough that it moves with light resistance.

Aim it squarely at its partner, sighting along the body of the sensor rather than eyeballing from across the garage. Move it slowly — the alignment window is narrower than people expect.

Watch for the light to go steady, then tighten the bracket while holding the sensor still. Tightening is where alignment is usually lost. Plug back in and test a full close cycle.

When alignment isn't the problem

Dirty lenses. Wipe both with a dry cloth. Dust films and cobwebs are enough.

Direct sun. Low winter sun shining into the receiver swamps the beam. If the fault only happens at a particular time of day, shade the sensor to confirm and fit a sun shield.

Damaged wiring. Staples driven through the wire, rodent damage, or a break where the wire runs along the track. If both lights are dead this is the likely cause.

Loose brackets. A sensor that drifts out of alignment every few weeks has a bracket that isn't holding. Replace the bracket rather than realigning it repeatedly.

Don't make forcing it a habit

Most openers close if you hold the wall button down, bypassing the sensors. That's there so you can secure the house when something has failed.

Used as a routine workaround, it removes the one feature that stops a door closing on a child or a pet. If you're holding the button every day, get the sensors fixed.