Misaligned or blocked safety sensors
The single most common cause of a door that won’t close (or reverses partway down) is the photo-eye safety sensors near the floor on each side of the door. If they’re misaligned, dirty, or something is blocking the beam between them, the opener will refuse to close the door as a safety measure. Check that both sensor lenses are clean and pointed directly at each other, with their indicator lights showing a steady (not blinking) signal.
Close-limit or travel settings out of adjustment
Openers have a "close limit" setting that tells the motor how far to travel before considering the door fully closed. If this is set incorrectly, the door may stop short of the floor or reverse before reaching it, interpreting normal resistance as an obstruction. This typically requires a professional adjustment rather than a DIY fix, since incorrect adjustment can create a safety issue.
Track obstructions or misalignment
Debris in the track, or a track that has shifted out of alignment, can cause enough resistance that the opener’s safety reversal feature kicks in. Visually inspect the tracks for visible obstructions, but leave physical track realignment to a professional, since forcing a misaligned track can cause the door to derail.
Broken spring masking as a closing problem
Less commonly, a door that seems to struggle on the way down (rather than refusing outright) can be related to spring tension issues rather than sensor or limit problems. This is a signal to stop operating the door and request a professional inspection rather than continuing to force it.
Frequently asked questions
Why does my garage door start closing and then go back up?
This is almost always the safety-reversal feature triggering — most commonly due to misaligned or blocked photo-eye sensors, but also possibly a close-limit setting issue or a track obstruction.
Is it safe to keep trying to close a door that keeps reversing?
Yes, a few repeated attempts to diagnose the cause (checking sensor alignment, clearing obstructions) is generally fine, but if it continues after basic checks, it’s worth having a professional look rather than forcing the issue.
Can dirty sensor lenses really stop a door from closing?
Yes — dust, cobwebs, or condensation on the sensor lenses can interfere with the beam enough to trigger a false obstruction reading, even with nothing actually blocking the path.