What Most People Get Wrong
Most Randolph homeowners assume a blinking sensor light means the sensor itself is broken. In a house built in the 1960s or 70s - and that's most of this area, since local stock runs 1938 to 1996 with a median build year of 1964 - the sensor is usually fine. What's moved is the slab or the track bracket it's mounted to. These houses have had sixty-plus years to settle, and the concrete floor of the garage doesn't settle evenly. One side of the slab can drop or heave a fraction of an inch relative to the other, and that's enough to tip a sensor eye out of alignment with its pair. People replace a $20 sensor when the real fix is a five-minute bracket adjustment. The other common mistake is blaming the opener logic board, pulling it apart, and finding nothing wrong because the board was never the problem. If your door reverses before it touches the floor, or refuses to close at all, check alignment first. It's the cheapest explanation and the most likely one in a neighborhood this age.
What to Check
Kneel at each sensor and look at the small LED on the unit - one should be steady, the other should match once the beam is clear. If either light is dim, flickering, or off, that's your drift. Next, run a finger along the bracket mount. On original 1960s and 70s track hardware, these brackets were often fastened directly into wood jamb trim that has since shrunk or warped with the seasons, and a loose screw lets the whole sensor rotate a degree or two - enough to break the beam path across a two-car opening. Check that the lenses are clean; garage dust and road salt tracked in over a Randolph winter film over the glass and scatter the beam even when the alignment is correct. Finally, look at the wire running to each sensor. In homes this old, that wire has usually been stapled, re-routed, or spliced at least once, and a nicked line causes intermittent faults that look exactly like misalignment but aren't. If you've checked all four of these and the door still won't behave, the bracket mount itself may have failed, not just loosened - that's a part swap, not an adjustment.
What Is Going On
Put together, what's happening in most of these calls is a chain: a slab that's moved slightly over sixty years, a bracket that was never designed to be re-leveled, and a cold climate that keeps nudging both every winter. None of that shows up as a dramatic failure - it shows up as a door that reverses for no clear reason, or won't close at all some mornings and works fine by afternoon once things settle. We can true up the brackets and re-aim the sensors in most cases without replacing hardware. Where we can't help is if the jamb wood itself has rotted or warped badly enough that the bracket has nothing solid to hold onto - at that point you're looking at frame repair before a sensor adjustment will hold, and that's a different job than we do on a sensor call. Worth knowing going in, so you're not surprised by the scope once we're under the door.
