Garage Door Sensor Repair in Ann Arbor, MI Photo-Eye Alignment

The reversal is a rule, not a malfunction

Federal law forces this behavior. Title 16 Part 1211 governs residential operators built for sale from January 1, 1993 onward, and section 1211.6 requires a secondary means of entrapment protection in addition to the motor's own force reversal. Section 1211.8 lists what satisfies it: an external photoelectric beam across the opening, or a sensing edge on the bottom of the door that trips at 15 pounds or less under section 1211.12. When the beam is broken, obscured or simply not received, the operator is designed to abandon the close and send the door back up. Sorting that from the other faults on the full list of repairs is the first thing worth doing, because a beam problem is cheap and a bound door is not.

Where the beam actually breaks here

Two eyes sit within six inches of the slab, which is precisely the height that collects everything a Michigan February produces. Brine spray dries into a gray haze on the lens and thins the received signal until the receiver drops out on a bright day and works at dusk. Meltwater running off a car pools around the bracket foot and refreezes, tipping the mount a degree or two. Condensation adds a third mechanism: warm humid air off a snow-covered car meeting a cold lens leaves droplets, and DASMA's sheet on garage door condensation describes exactly that combination of a warm, humid garage and a colder surface. A lens wiped with a dry cloth in October behaves differently in January.

Wiring is the failure people never look at

The two eyes are wired in series back to the motor head with light two-conductor bell wire, usually stapled along the jamb and up into the ceiling. A staple driven a millimeter too far pinches the insulation, and moisture from a detached garage's freeze and thaw cycling finishes the short. In the detached garages behind the narrow lots of the Northside, where the neighborhood's school building dates to 1939, that run is often long, spliced at least once, and sitting in bare wire nuts inside an unheated space. Rodents chew low-voltage wire in the same buildings. A pinched conductor and a dirty lens produce an identical symptom at the wall button, and only one of them is fixed with a rag.

Read the indicator lights before anything comes apart

Most brands put a small LED on each eye. A steady light on both usually means the pair is aligned and communicating; a light out or flickering on the receiver side means it is not seeing its partner. Some heads also blink a count on the motor unit that maps to a sensor fault in the manual taped inside the cover. Note which light misbehaves and whether it changes when the sun angle changes, because a receiver that fails only in the late afternoon is a different repair from one that never lights at all. On a 1936 Cape Cod near Gardner Avenue in Lower Burns Park, a garage that has settled will also throw alignment slowly out over a season, which reads as an intermittent fault.

What the visit corrects

Lenses are cleaned, brackets are re-aimed and locked, and the wire is traced end to end rather than jiggled at the head. Suspect splices are cut out and remade, and staples that have bitten through insulation get replaced with insulated clips. Alignment is verified with the door cycling, not by eye. Then the reversal is tested deliberately by breaking the beam mid-travel and confirming the door returns fully up. If the door also stalls without the beam involved, the fault is drag in the door and the honest answer is that the sensors were never the problem. That is where a door that will not close for other reasons or a full safety inspection picks the job up.