You press the button, the door starts to close, and then it stops and goes right back up. The opener light flashes a few times. You try again, and it does the same thing. In most cases, the problem is not the opener at all. It is the pair of small safety sensors mounted near the bottom of the door tracks.
Garage door sensors are simple, but they are also very sensitive. A bit of dust, a bumped bracket, or even the afternoon sun can stop them from working. If the sensors check out and the opener still misbehaves, our guide on a garage door opener not working covers the bigger picture. This article focuses on the sensors themselves: how they work, why they fail, and how to fix them in a few minutes.
Quick Answer
If your garage door sensor is not working, first check the small lights on both sensors. If one light is off or blinking, the sensors are blocked, dirty, or misaligned. Remove anything in the door’s path, wipe both lenses with a soft cloth, and adjust the sensors until both lights glow steadily. If the lights stay off, check the wires for damage or loose connections.
How Garage Door Safety Sensors Work
Every automatic garage door opener sold in the United States since 1993 has been required to include a safety reversing system. On most openers, that system is a pair of photo-eye sensors mounted on each side of the door, no more than six inches above the floor.
One sensor, the sending unit, shoots an invisible infrared beam across the opening. The other sensor, the receiving unit, picks it up. As long as the beam is unbroken, the opener will close the door. If anything crosses the beam, such as a child, a pet, a bike, or a box, the opener stops the door and reverses it.
That safety feature is exactly why a small sensor problem can keep your door from closing. The opener cannot tell the difference between a toddler and a cobweb. If the beam is broken for any reason, the door will not close.
What the Sensor Lights Mean
Most sensors have a small LED light on each unit. The colors vary by brand, but the pattern is usually similar:
- Sending sensor: usually amber or yellow. It should glow steadily whenever the opener has power.
- Receiving sensor: usually green. A steady light means it is getting the beam. A blinking or dark light means the beam is blocked or the sensors are out of line.
- Both lights off: a power or wiring problem.
Many openers also flash the light on the motor unit a set number of times when there is a sensor fault. On a lot of Chamberlain and LiftMaster openers, for example, ten flashes point to a sensor problem. Our Chamberlain garage door opener repair article explains more of these flash codes.
7 Common Reasons Garage Door Sensors Stop Working
1. Something Is Blocking the Beam
Start with the obvious. A trash can, a broom, a garden hose, or a storage bin sitting just inside the door can block the beam. So can leaves or a spider web stretched across the lens.
2. Dirty Lenses
Dust, pollen, and grime build up on the lens over time. In humid weather, condensation can also fog the lens. A dirty lens weakens the beam until the receiving sensor no longer picks it up.
3. Misaligned Sensors
This is the most common cause. The sensors sit low, right where they get bumped by feet, bikes, lawn mowers, and car tires. Even a small shift can send the beam off target. Loose mounting brackets and vibration from the door can also move them out of line over time.
4. Direct Sunlight
On doors that face east or west, strong sunlight can shine straight into the receiving sensor and overpower the infrared beam. The door may close fine most of the day and then refuse to close in the early morning or late afternoon. This is a common complaint during long Texas summers in areas like Jersey Village, where garages often face the full afternoon sun.
5. Damaged or Loose Wiring
Sensor wires run along the wall from each sensor up to the opener. They can be pinched by staples, chewed by rodents, cut during a renovation, or loosened at the terminals on the opener. If both sensor lights are off, wiring is the first thing to check.
6. Moisture and Corrosion
Water can get into the sensor housing during heavy rain, flooding, or a wash-down of the garage floor. Over time, corrosion on the wires or inside the sensor can cause the lights to flicker or fail.
7. A Failing Sensor or Opener Board
Sensors do wear out. So does the circuit board inside the opener that reads them. If you have ruled out everything else, one of these parts may need replacing
How to Fix Garage Door Sensors Step by Step
- Clear the path. Remove anything near the bottom of the door on either side.
- Clean both lenses. Wipe them gently with a soft, dry microfiber cloth. Do not use harsh cleaners that can scratch the lens.
- Check the lights. Note whether each sensor light is steady, blinking, or off.
- Realign the sensors. Loosen the wing nut or screw holding the sensor to its bracket. Slowly pivot the sensor until the receiving light turns solid. Then tighten it again without moving it.
- Use a level or string if needed. Both sensors should sit at the same height and point straight at each other. A tight string stretched between them can help you line them up.
- Inspect the wires. Follow each wire from the sensor to the opener. Look for staples pressing into the wire, cuts, or loose connections at the opener terminals.
- Test the door. Close the door, then wave an object through the beam while it closes. It should stop and reverse.
If the wiring looks damaged or the lights still will not stay on, it is time for garage door opener repair. A technician can test the sensor circuit and the opener board to find the faulty part.
How to Stop Sunlight From Interfering
If the problem only happens at certain times of day, sunlight is the likely cause. Try these fixes:
- Swap the sensors so the receiving unit sits on the side that gets less direct sun.
- Install a small sun shield or a short piece of tube over the receiving sensor to block glare.
- Make sure the sensors are well aligned, since a weak beam is easier for sunlight to overpower.
Can You Close the Door If the Sensors Are Not Working?
On many openers, yes. Press and hold the wall button until the door is fully closed. This constant-pressure mode lets the door close even with a sensor fault. If you let go early, the door will stop or reverse. Watch the door the entire time it is moving.
This is a short-term workaround only. Never tape over the sensors, remove them, or wire them together to bypass them. They are there to keep people and pets from being trapped under a closing door, and disabling them is both unsafe and against the opener’s safety design.
When Garage Door Sensors Need to Be Replaced
Replace the sensors if the lights will not come on even with good wiring, if the housing is cracked, or if corrosion has damaged the internal parts. Replacement sensors must match your opener brand and model. Sensors from one brand usually do not work with another. Brand-specific openers, like the ones covered in our LiftMaster garage door repair guide, have their own compatible sensor kits.
Get Garage Door Sensor Repair in Houston, TX
If you are searching for garage door repair near me because your door keeps reversing, the sensor light will not stop blinking, or the opener will not close the door at all, Ultra Garage Door Services can help the same day. We provide garage door repair in Houston, TX and nearby cities, including sensor alignment, sensor replacement, wiring repair, and opener board diagnosis for residential and commercial doors.
Get your door closing safely again today. Request a free estimate or call Ultra Garage Door Services at (346) 630-9023. First-time customers get 10% off their first service.
Frequently Asked Questions
Why is my garage door sensor blinking?
A blinking sensor light usually means the beam is blocked or the two sensors are not lined up. Clear the path, clean both lenses, and adjust the sensors until the light stays solid.
Why does my garage door go up instead of closing?
The opener reverses the door when the safety sensors detect an obstruction or lose their signal. Misaligned or dirty sensors are the most common reason. Incorrect force or travel settings can also cause it.
Can sunlight affect garage door sensors?
Yes. Direct sunlight hitting the receiving sensor can drown out the infrared beam, especially in the early morning or late afternoon. Swapping the sensor sides or adding a sun shield usually solves it.
How much does it cost to fix garage door sensors?
A simple realignment or cleaning costs little or nothing if you do it yourself. Replacing sensors or repairing damaged wiring costs more, depending on the opener brand and the work needed. A technician can give you an exact estimate after testing the system.
Do both garage door sensors need to be replaced at the same time?
Not always, but it is common. Most replacement sensors are sold as a matched pair, and replacing both keeps them compatible and evenly matched in age.
