Start with the safety sensors
If your garage door starts to close and then reverses back up, the cause is almost always the safety sensors — the two small photo-eye units mounted near the floor on each side of the door. They send an invisible beam across the opening, and if anything interrupts that beam, the door reverses to avoid crushing it.
Sensors are the first thing to check because they cause the majority of won't-close problems and the fixes are simple and free.
A blinking light on the opener motor is often a sensor code. Most openers blink a set number of times to tell you the sensors are the issue.
How to diagnose a door that won't close
Work through these checks in order. Most won't-close problems are solved within the first few steps.
- 1
Clear the sensor path
Look along the floor between the two sensors. A bin, a bike, a coiled hose, even a pile of leaves can break the beam. Remove anything in the opening.
- 2
Clean the sensor lenses
Wipe both sensor lenses gently with a soft, dry cloth. Dust, cobwebs, and condensation on the lens can block the beam just as well as a physical object.
- 3
Check the sensor alignment
Each sensor has a small indicator light. Both should glow steadily. If one is off or flickering, the sensors are out of alignment — gently adjust one until both lights are solid.
- 4
Inspect for a track obstruction
Look up the tracks on both sides. A bent track section, a dislodged roller, or debris can physically stop the door partway down.
- 5
Test the remote and wall button
Try closing the door with the wall button instead of the remote. If the wall button works but the remote does not, the issue is a remote battery or remote programming, not the door.
- 6
Check the close-limit setting
If the door closes then immediately reopens, the opener's close-limit setting may be off, telling the door it has hit the ground too early. This is an adjustment screw on the opener — consult the opener manual or call a technician.
The other common causes
Bent or misaligned track
If a track section is bent or has pulled away from the wall, the door binds and stops. Minor debris you can clear; a genuinely bent track needs a technician.
Worn or broken rollers
A roller that has cracked or jumped out of the track will stop the door partway. Rollers are a wear part and replacing them restores smooth travel.
Damaged cables
Frayed or snapped lift cables prevent the door from travelling correctly. Cables are under tension and should only be handled by a technician.
Close-limit and force settings
Openers have settings that tell the door how far to travel and how much resistance is normal. If these drift out of calibration, the door may stop short or reverse. A technician can recalibrate them quickly.
When to call a professional
Sensor cleaning, alignment, and clearing the door's path are all safe to do yourself. But call a technician if the problem is a bent track, broken rollers, damaged cables, or opener limit settings you are not comfortable adjusting.
A door that won't close is also a security and safety issue — an open garage is an open invitation, and a door that behaves unpredictably around children or pets needs prompt attention. If the simple checks don't solve it, don't leave it.
