Garage door won't close: step-by-step diagnosis

Updated November 2, 2026. Every manufacturer code and safety rule on this page links to its source below.

Short answer

The most common reason is the safety sensors (photo eyes) at the bottom of the door tracks: something is in the beam, a lens is out of line, sunlight is hitting it, or a wire is damaged. After that, check for lock or vacation mode, the travel limits, and the door itself. Federal rules have required this kind of entrapment protection on residential openers made since January 1, 1993, so never disable the sensors to get the door down.

Start with the symptom

Match what you see to the step to start with
What you see	Most likely	Start at
Door does not move, opener lights flash	Safety sensors (Chamberlain: 10 flashes)	Step 3
Door moves an inch or two and goes back up	Sensor wires reversed or shorted (LiftMaster code 1-2)	Step 4
Wall button works, remote does not	Lock or vacation mode on	Step 2
Nothing works from anywhere	No power to the opener	Step 2
Door goes most of the way down, then reverses	Close limit, force or the door	Reverses guide
Door stops before it reaches the floor	Close limit setting, shorted wires or binding	Step 5
Opener is blinking a code	Depends on brand	Blink codes

Safety first

Keep people and pets out of the doorway while testing. If you see a broken spring, a loose or frayed cable, or rollers out of the track, stop. DASMA's checklist says not to operate a door with a broken spring until it is replaced, and not to remove, repair or adjust springs, cables or their brackets yourself.

Step 1: watch what the door does

Close the door with the wall control and watch. Count any flashes on the opener light or the motor unit. Note whether the door does not move, moves a little and returns, or travels most of the way and reverses. The table above sends you to the right step. If your opener shows a numbered code, look it up in our blink code guide first.

Step 2: rule out power and lock mode

Power. Genie's troubleshooting chart suggests plugging a lamp into the opener's outlet. If the lamp does not light, check the breaker, fuse or GFCI before blaming the opener.
Lock or vacation mode. If the wall control works but remotes do not, the lock feature is likely on. Chamberlain describes a LOCK button on its door controls, the Genie Excelerator shows 8 blinks for a locked wall console, and Linear's LDCO850 shows 5 flashes for vacation mode. Turn it off and try the remote again.

Step 3: clear and align the safety sensors

The sensors sit on each side of the door opening, near the floor. One sends an infrared beam and the other receives it. If the beam is broken, the opener will not close the door.

Remove anything in the doorway: bins, leaves, a cord, a spider web on a lens.
Wipe both lenses clean.
Check the lights. On Chamberlain and LiftMaster sensors, the sending eye has an amber LED and the receiving eye a green LED. Both should glow steadily.
If a light is off or flickering, loosen the sensor's wing nut, point the lenses straight at each other, and tighten it once the LED is steady. Chamberlain says to make sure they face each other directly and are level.
Check the height. DASMA says the beam must be no higher than 6 inches above the floor, and within 6 inches of the door's path. Chamberlain's guidance puts the sensors 4 to 6 inches up.
If the door fails only at certain times of day, suspect sunlight. Chamberlain notes sun on the receiving eye can block the beam.

Do not move the sensors higher to stop false trips. DASMA explains the 6-inch limit exists so a small child cannot crawl under the beam.

Step 4: check the wiring

Reversed or shorted sensor wires (LiftMaster and Chamberlain code 1-2) often make the door move an inch or two and go back up. Chamberlain says wire colors must match at both ends: white to white, black-striped to black-striped.
Staples and pinches. Genie and Linear both point to staples cutting through wall-control or sensor wire insulation. Look along the run, especially where wire is stapled to framing.
Both sensor lights dark. Chamberlain says damaged wiring is likely; if new wire does not bring a steady glow, the sensors themselves may need replacing.

Step 5: check the travel limits and the door

If the door starts down and stops before it is closed, Genie's Excelerator chart lists three checks: the close limit setting, shorted wires, and the door binding. Linear shows 6 flashes when the up and down limits are set too close together. Reprogram limits only with your model's manual in hand, then retest the safety reversal.

Then look at the door itself, from inside, with the door closed. DASMA tells homeowners to check that rollers are in the track, that hinges and brackets are attached, and to look (without touching) for loose cables or other changes in the spring system. A door that is heavy, binds, or will not stay put when partly open needs a technician, not more opener force. Our garage door sounds guide helps describe what you hear.

Step 6: close it safely if you must

Hold the wall control. On many LiftMaster and Chamberlain openers, pressing and holding the door control push bar until the door is down will close it with a sensor fault. Chamberlain notes openers and logic boards made after February 3, 2022 no longer have this feature.
Manual release, with care. Linear's manual says to use the emergency release only when the door is closed when possible, because weak or broken springs can make an open door come down faster. DASMA adds that a door may begin to move unexpectedly once it is disconnected. If the door is open and you suspect a spring problem, leave it and call a pro.

Step 7: retest before you trust it

DASMA recommends testing the safety systems monthly, and after any fix:

Photo-eye test. Start the door closing, then pass an object through the beam. The door must reverse and return to fully open.
Contact reversal test. Lay a 2x4 flat on the floor under the center of the door (1½ inches tall) and close the door on it. It must reverse. Federal rules require residential openers to reverse within 2 seconds of contact with an obstruction.

If either test fails, do not use the opener until it is serviced.

Frequently asked questions

Why won't my garage door close but the light blinks?

On LiftMaster and Chamberlain openers, Chamberlain says main lights that flash 10 times mean a safety reversing sensor problem. Clear the beam and realign the sensors until both sensor LEDs are steady. Other brands use their own blink codes, listed in our blink code guide.

How high should garage door safety sensors be?

No higher than 6 inches above the garage floor. DASMA says this is so a small child cannot crawl under the beam, and Chamberlain's install guidance gives 4 to 6 inches.

Why does my garage door close with the wall button but not the remote?

Check the wall control's LOCK or vacation feature first, since it blocks remotes. Chamberlain, Genie (Excelerator 8 blinks) and Linear (5 flashes) all describe this. If lock is off, the remote battery or programming is next.

Can sunlight stop a garage door from closing?

Yes. Chamberlain says sunlight can interfere with the infrared beam between the sending sensor (amber LED) and receiving sensor (green LED), so the opener thinks the path is blocked.

How do I close a garage door when the sensors are not working?

On many LiftMaster and Chamberlain openers you can press and hold the wall control push bar until the door is fully down; Chamberlain notes openers and logic boards made after February 3, 2022 no longer have this feature. Otherwise use the red manual release, preferably only with the door already closed, and get the sensors fixed. Never remount or bypass the sensors.

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Sources

Codes and rules are paraphrased from these documents. Charts vary by model and software version, so your owner's manual wins if it disagrees with this page.

Why do the lights on my garage door opener flash and my door will not close, Chamberlain Group support (LiftMaster, Chamberlain), as of 2026.
Garage Door Opener Diagnostic Codes, Chamberlain Group support, as of 2026.
How to troubleshoot the safety reversing sensors when one LED is off or flickering, Chamberlain Group support, as of 2026.
How should I position my safety reversing sensors, Chamberlain Group support, as of 2026.
TDS-364, Installation Location of Photoelectric Sensors on Residential Garage Doors, DASMA (Door & Access Systems Manufacturers Association), as of 2026.
TDS-369, FAQ Regarding Automated Residential Garage Door Systems, DASMA, as of 2026 (rev. 2020).
TDS-167, Residential Sectional Garage Door and Electric Operator Checklist, DASMA, as of 2026 (rev. 2023).
TDS-174, Checking a Residential Sectional Garage Door for Damage, DASMA, as of 2026.
Genie Excelerator Self-Diagnostic and General Troubleshooting charts, The Genie Company, as of 2026.
Linear LDCO850 Homeowner's Manual (safety instructions and troubleshooting), Nortek Security & Control (Linear), as of 2026.
16 CFR 1211.1 and 1211.7, Safety Standard for Automatic Residential Garage Door Operators, U.S. Code of Federal Regulations (via Cornell LII), as of 2026.