Leaving It Alone
A door that reverses for no reason, or a light that blinks instead of staying solid, is annoying but it's not an emergency. Most Bethesda houses on this side of town went up between 1938 and the early 2010s, with the bulk of the stock dating to the 1960s and 70s. That means a lot of these garages still have their original wood jambs, and wood moves with the seasons in a way steel studs don't. If the sensors are close but not quite aligned, and the door still closes most of the time, you can usually wait a week and see if it's getting worse before you touch anything. Tightening a bracket that isn't actually loose can strip the screw hole in old, dried-out jamb wood, which turns a five-minute fix into a bracket replacement. The honest answer is that a little bit of blinking-light annoyance doesn't always need same-day attention. What does need attention is a door that won't close at all, or one that closes and then reverses hard every single time - that's a different problem and it's covered further down.
What Is Going On
When a sensor drifts, the eyes are no longer pointed at each other dead-on, so the beam that's supposed to run flat across the opening clips the edge of the receiving lens instead of hitting it square. The opener reads that as an obstruction, even though nothing is in the way, and it either refuses to close or reverses midway down. On older Bethesda houses with original one-piece or early sectional doors, the sensor brackets are often the thin stamped-metal kind that bends slightly every time someone bumps it with a bike or a trash can, which speeds up the drift that frost heave starts. You can usually tell the difference: a bent bracket shows a visible kink, while frost-driven drift shows no damage at all - the hardware just isn't aimed right anymore. Dirt and spiderwebs across the lens cause the same symptom and get blamed first, so wipe both eyes with a dry cloth before assuming it's alignment.
When It Stops Being a DIY Job
If you've wiped the lenses, loosened the wing nuts, and nudged both sensors until their indicator lights go solid, and the door still won't behave, the problem usually isn't the sensors at all - it's the bracket mount failing in jamb wood that's too soft to hold a screw anymore, which is common in a house built before the 1980s. At that point, re-aiming the sensor doesn't fix anything because the bracket itself can't hold the aim once you walk away. That's a repair job, not an adjustment, and it's worth having someone look at the actual wood before replacing a sensor that was never the problem. We don't recommend drilling new holes into deteriorated jamb trim as a patch - if the wood's gone soft, the fix is a new mounting surface, and that's worth getting done right the first time rather than twice.{"/":true}
