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If your garage door won't close, or starts down and then reverses back up, the cause is usually the safety sensors. They're the two small "photo eyes" near the bottom of the tracks. When the sensors are dirty, knocked out of alignment, blinded by the sun, or have a loose wire, the opener thinks something is in the way and refuses to close. Other common causes are the close-force or limit settings, an obstruction in the track, or a broken spring or cable. That last one needs a professional.

This guide walks you through what to check, in order, from the 30-second fixes to the signs it's time to call for service.

First: safety

Before you start, keep a few rules in mind:

  • Don't stand or walk under a moving door, and keep kids and pets clear.
  • Don't touch the springs, cables, or bottom brackets. They're under extreme tension. If you see a broken spring or a loose cable, stop and call a technician.
  • Don't disable or bypass the sensors to get the door to close. They're there to keep the door from closing on a person, pet, or car.

Under the UL 325 safety standard, automatic garage door openers must have an entrapment-protection system, usually photo-eye sensors, that reverses the door when something is in its path. The Door & Access Systems Manufacturers Association explains why the eyes have to sit low in its Six-Inch Rule. Those sensors are doing their job when they stop the door. The goal is to figure out why they think something is there.

Step 1: Look at the sensor lights

Each sensor has a small indicator light. On most LiftMaster and Craftsman openers:

  • The sending sensor glows amber or yellow.
  • The receiving sensor glows green when it can "see" the other sensor.

If the green light is off, dim, or flickering, the sensors aren't lined up or something is blocking the beam. Many openers also tell you about a sensor problem by flashing the opener's light bulbs several times when you try to close the door. Some models also blink an LED on the motor unit or show a diagnostic code. Check your owner's manual for what your model's flashes mean.

Other brands use different colors, but the idea is the same: one steady light on each side means the beam is connected.

Step 2: Clean the lenses

This is the easiest fix and one of the most common. Dust, cobwebs, pollen, lizard droppings, and water spots build up on the lenses, especially in a South Florida garage that stays open during yard work.

Wipe each lens gently with a soft, dry cloth or a microfiber cloth. Skip harsh cleaners and anything abrasive. Then try closing the door again.

Step 3: Check for anything in the beam's path

The beam runs a few inches above the floor across the entire opening. Look for:

  • A trash can, kayak, bike tire, or box near the track
  • Tall grass, a plant, or a bag of mulch near the opening
  • A garden hose or extension cord hanging down
  • Spider webs strung across one of the sensors

Even something small can break the beam.

Step 4: Realign the sensors

Sensors get bumped by cars, bikes, brooms, and kids. Even a small nudge can break the connection.

  1. Check that both sensors are mounted at the same height and face each other directly. Per the six-inch rule, the photo eyes should sit about 4 to 6 inches above the floor and never higher than 6 inches.
  2. Loosen the wing nut or screw on the bracket of the sensor whose light is off or flickering.
  3. Slowly pivot the sensor until its indicator light turns solid.
  4. Tighten the bracket without moving the sensor.
  5. Test the door.

If the bracket itself is bent, gently straighten it or replace it so the sensor sits square to the opening. A string line from one sensor to the other can help you check alignment.

Step 5: Rule out the sun

In South Florida, direct sunlight is a very common cause of a door that won't close at certain times of day. If your garage faces east or west, low morning or late-afternoon sun can shine straight into the receiving sensor and "blind" it, so it can't see the beam.

A quick test: if the door closes fine at midday or after dark but not at sunrise or sunset, the sun is probably the problem. Solutions include swapping the sending and receiving sensors so the receiver faces away from the sun, or adding a shade or sun shield. We cover this in detail in The Effect of Sunlight on Garage Door Sensors.

Step 6: Check the wiring

Sensor wires run along the wall or ceiling back to the opener. Look for:

  • Wires that are cut, pinched, or chewed (rodents and lawn trimmers are common culprits)
  • Loose connections at the sensor or at the opener terminals
  • Corroded staples or splices, which are common in humid, coastal garages

Damaged low-voltage wiring can make a sensor light flicker on and off. If you find damage, the safest fix is usually new sensor wire or a new sensor kit installed by a technician.

Step 7: Check the remote, wall button, and lock mode

If nothing happens at all when you press the button, check:

  • The wall control's lock or vacation mode. Many wall controls have a lock button that disables remotes. If the lock light is blinking, turn it off.
  • Remote batteries. Try the wall button. If the wall button works and the remote doesn't, replace the battery or reprogram the remote. See our guide to programming garage door remotes and keypads.
  • Power. Make sure the opener is plugged in and the outlet works. Check the GFCI outlet and the breaker.

Step 8: Check the close limit and force settings

If the door goes all the way down, touches the floor, and then reverses back up, the close limit or force setting may be off. That's especially likely after a power surge, a new floor coating, or a new bottom seal. The opener thinks the door hit an obstruction when it's really just hitting the ground.

Newer openers set limits with buttons on the motor unit. Older ones use adjustment screws. Follow your owner's manual exactly, change things in small steps, and test the auto-reverse afterward. To test it, lay a 2x4 flat on the floor under the door. The door should reverse when it touches the board. If you aren't comfortable doing this, it's a quick service call.

Step 9: Look at the tracks, rollers, and hardware

If the door moves unevenly, jerks, binds partway down, or one side sits lower than the other, the problem may be mechanical:

  • Bent or misaligned tracks from a car bump
  • Worn or broken rollers
  • A frayed or loose cable
  • A broken spring. You may have heard a loud bang, and the door may feel very heavy.

These are not DIY repairs. A door with a broken spring or cable can drop suddenly. A door that has come out of its track can fall. If you see any of these, stop using the door and call for service. Learn more in Broken Garage Door Spring? What South Florida Homeowners Need to Know and on our off-track garage door repair page.

How to close the door in an emergency

If you need to secure your home and can't wait for service, most openers let you close the door by pressing and holding the wall button until the door is fully down. This bypasses the sensors for that one close, so watch the door the whole way and make sure the opening is clear.

If the opener has no power, you can pull the red emergency release cord and close the door by hand. Only do this if the springs and cables are intact and the door feels balanced. If the door feels very heavy, leave it and call for help.

When to call a professional

Call a garage door technician if:

  • Cleaning and realigning the sensors didn't fix the problem
  • The sensor wiring is damaged
  • You see broken springs, frayed cables, bent tracks, or a door hanging crooked
  • The auto-reverse safety test fails
  • The opener hums but the door doesn't move
  • The door closes at different points each time

Frequently asked questions

Why does my garage door go down and then go back up? Usually the safety sensors are blocked, dirty, or misaligned, or the close limit is set so the door "hits" the floor and reverses. Clean and align the sensors first, then check the limit setting.

How do I know if my garage door sensors are misaligned? The indicator light on one or both sensors will be off, dim, or flickering instead of steady. Many openers also flash their light bulbs when you try to close the door.

Can sunlight stop a garage door from closing? Yes. Direct sun shining into the receiving sensor can blind it, especially on east- or west-facing garages in South Florida. Shading the sensor or swapping which side the receiver is on usually solves it.

Is it safe to bypass garage door sensors? No. The sensors are a required safety feature that keeps the door from closing on people, pets, and cars. Hold the wall button for an emergency close only, and get the sensors repaired.

How much does it cost to fix garage door sensors? It depends on whether the sensors need cleaning and alignment, new wiring, or replacement. At Ultra Garage Doors, repairs start at $70, and we quote the price before any work begins.

Still won't close? We can help today

Ultra Garage Doors offers same-day garage door repair across Broward and Palm Beach County, with 24/7 emergency service when your door won't close and your home isn't secure. Our trucks carry sensors, wiring, rollers, cables, and springs, so most problems are fixed in one visit.

Call 561-494-4070 or request service online. Learn more about our garage door repair and automatic garage door opener services.