🔧 Fix-It Guide · free checks first
Why Won't My Garage Door Close?
Honest diagnosis, free checks first, and a straight answer about when it's a pro job. No teaser fees, no scare tactics — that's the whole point of this site.
Honest diagnosis, free checks first, and a straight answer about when it's a pro job. No teaser fees, no scare tactics — that's the whole point of this site.
Look at both sensors near the floor. On LiftMaster and Chamberlain, the amber sending light should be on and the green receiving light steady. A dark or flickering green light means the beam is broken. On Genie, a repeatedly blinking red LED signals misalignment or interference. This one glance usually identifies the whole problem.
Remove anything between the sensors — tools, trash cans, leaves, a thick cobweb. Wipe both lenses gently with a soft dry cloth; a film of dust or a splash of mud is enough to blind them. Check that nothing hangs from the door itself, like a dangling rope or seal flap, that swings through the beam mid-travel.
Loosen the wing nut on the misbehaving sensor, aim it squarely at its partner, and watch the indicator light while you adjust. When the green (or steady red on Genie) light holds solid, tighten the wing nut without twisting the sensor. Bumped brackets are the single most common cause of a door that will not close.
Follow the thin bell wire from each sensor up the wall and along the ceiling to the opener terminals. Look for staple pinches, nicks, chew marks, or a wire pulled loose at either end. Push connections firmly into the opener terminals. If the sending sensor's light is completely dark, power or wiring is interrupted somewhere on that run.
To secure the garage while you troubleshoot, press and hold the wall button until the door fully reaches the floor — releasing early reverses it. This built-in UL 325 override works only from the wall control, never the remote. Treat it as a temporary measure and restore the sensors promptly.
The two sensors near the floor project an invisible infrared beam across the door opening; if anything breaks the beam while the door closes, the opener reverses. Federal safety rule 16 CFR 1211 has required this entrapment protection on openers built since 1993, so nearly every working opener has them. On LiftMaster, Chamberlain, and Craftsman systems, the sending sensor shows an amber or yellow light that stays lit regardless of alignment, and the receiving sensor shows a green light that glows steadily only when the beam connects. Green light off or flickering means misalignment, a blocked lens, or a wiring fault. On Genie Safe-T-Beam systems, one sensor shows green and the other red; a red LED blinking repeatedly signals trouble — in Genie's self-diagnostic scheme, two blinks indicates misalignment or obstruction and three blinks indicates infrared interference. Whatever the brand, a steady light on both sensors is the goal, and a dark or blinking one tells you where to work.
Timing is diagnostic. If the door reverses the instant it starts to close — or refuses to move and the opener light just flashes — that is the sensor circuit rejecting the close command; the opener will not close on its own authority without a healthy beam. If the door closes most of the way and reverses near the floor, the sensors are probably fine and you are instead looking at a close-force or travel-limit problem, or something physical the door touches on the way down, which we cover on the reversing page. So watch one full cycle before touching anything. For instant reversals, work the sensor checklist: clear anything in the beam path (a rake handle, a garbage can, a cobweb thick enough to matter), wipe both lenses with a soft cloth, and check that each sensor points squarely at the other. Sensors mount on wing-nut brackets that go out of square when a bike or broom bumps them — a nudge of a few degrees is enough to break the circuit.
On Chamberlain-family openers — LiftMaster, Chamberlain, and most Craftsman units — the main opener light flashing ten times is the specific signal that the safety sensors are blocked, misaligned, or miswired. It is the opener telling you exactly where to look, so do not start by suspecting the remote or the motor. Check the beam path, clean the lenses, and re-square the brackets until the receiving sensor's green LED holds steady. If the green light will not come on at all, inspect the thin wires running from each sensor up to the motor unit: staples pinch them, ladders snag them, and connections at the opener terminals work loose. Newer LiftMaster models also blink out precise diagnostic codes on up and down arrow LEDs at the motor head — for example, one flash then four flashes indicates misaligned or obstructed photo eyes, while codes in the one-then-two range point to shorted or reversed sensor wiring. Your owner's manual (or a search for your model number plus the code) decodes the exact pair.
Yes, and it is a deliberate design feature, not a hack. Openers built to UL 325 allow a constant-pressure close: press and hold the wall button (not the remote — remotes will not do this) and keep holding it until the door reaches the floor. If you release early, the door reverses. This works because a human watching the door is an acceptable substitute for the beam, per the standard. Use it to secure your garage tonight — but treat it as a bridge, not a lifestyle. The sensors exist because 54 children died in door entrapments in the decade before the 1993 federal rule, and a door that only closes under held pressure is a door with disabled protection for anyone else in the household who does not know. Fix or realign the sensors promptly, and never bypass them permanently by wiring them together or taping them facing each other; that defeats the entire safety system.
It can, and it is one of the odder honest answers in this business. The receiving sensor watches for a specific infrared signal from the sender, and direct low-angle sunlight — typically late afternoon on west-facing garages, or morning on east-facing ones — can flood the receiver with enough infrared to drown the beam out. The giveaway: the door refuses to close only at certain times of day and behaves perfectly otherwise. Genie's diagnostics even call this out with a distinct blink code for interference. Free fixes first: swap the two sensors side to side so the receiver sits on the shaded side (keep the wiring polarity as the manual directs), or shield the receiving lens with a short cardboard or PVC tube a few inches long, like a lens hood on a camera. Both approaches are legitimate and preserve the safety function. If sun trouble persists across the whole day, the receiver itself may be degrading, and sensor pairs are inexpensive standard parts a tech can swap quickly.
If the door closes fully, touches the floor, then pops back open, the opener may think the floor is an obstruction. Openers learn a down travel limit — how far to move before expecting the floor. If the limit is set slightly long, the door presses into the concrete, the force sensor reads the resistance as a trapped object, and the opener reverses, exactly as 16 CFR 1211 requires it to. This shows up after a new floor, a new weather seal, new rollers, or in cold snaps when the door and seal stiffen. The free fix is an adjustment: on older units, a screwdriver turn on the down-limit dial at the motor head; on newer LiftMaster and Genie models, a button-driven relearn sequence in the manual. Adjust in small increments and re-test. What you should not do is crank up the close force to bully through it — force settings exist to protect people, and a door that needs high force to close has a mechanical problem worth diagnosing.
That is the constant-pressure override built into UL 325 openers, and it activates when the safety sensor circuit is unhappy. The door is telling you the photo eyes are blocked, misaligned, or miswired. Check the sensor lights near the floor and re-square or clean them; the held-button trick is a stopgap, not a fix.
Usually neither is bad. On LiftMaster-family systems the amber sending light stays on regardless, while the green receiving light only glows when the beam connects — so a dark green light typically means misalignment, a dirty lens, or an obstruction, not a dead part. Realign first; replace only if no aiming brings the light back.
Indirectly, yes. Water droplets or snow spray on a sensor lens can scatter the beam, cold can pop a marginal alignment out of tolerance, and a frozen or stiff bottom seal can trigger the floor-contact reversal. Wipe the lenses, confirm steady sensor lights, and if the door reverses at the floor only in cold weather, the down limit likely needs a small seasonal adjustment.
No. They are federally required entrapment protection under 16 CFR 1211, most openers simply refuse automatic closing without a healthy sensor circuit, and removing them puts children, pets, and anyone under the door at real risk. Sensors are inexpensive, standardized parts; fixing them is faster than fighting them.
Talk to a local garage-door pro now. Free to call, no obligation, honest answers — the way it should be.