Few garage door problems are as frustrating as a door that goes down a few inches, then reverses back up for no visible reason. Nine times out of ten, the explanation is sitting a few inches off the floor on either side of the door: the safety sensors.
The good news is that sensor problems are among the safest garage door issues for a homeowner to check. This guide explains how the sensors work, what the blinking lights mean, why late-afternoon sun in the Sacramento area causes trouble, and when it is time to call for help.
How Garage Door Safety Sensors Work
Safety sensors, often called photo-eyes, come in a pair. One unit sends an invisible infrared beam across the garage opening, and the other receives it. As long as the beam is unbroken, the opener knows the path is clear.
If anything interrupts that beam while the door is closing, such as a child, a pet, a bike, or a box, the opener stops and reverses the door. Federal safety standards have required this kind of entrapment protection on residential openers for decades, and it is one of the most important safety features in your home.
Because the system is designed to fail safe, a door that will not close is the sensors doing their job when they think something is wrong.
What the Blinking Lights Mean
Most sensors have a small LED on each unit. The exact colors vary by brand, but the general pattern is similar:
- Both lights steady: the sensors are powered and can see each other.
- Receiving light blinking or off: the beam is blocked or the sensors are out of alignment.
- Both lights off: the sensors may not be getting power, which can point to wiring or the opener.
Many openers will also flash the overhead light or blink a light on the motor unit when the sensors are not happy. Your owner's manual can tell you the exact codes for your model.
Why Low Sun Can Blind Your Sensors
Here is something many Sacramento-area homeowners discover the hard way. If your garage faces west, strong late-afternoon sun can shine directly into the receiving sensor. That bright light can overwhelm the infrared beam, so the opener thinks something is blocking the door.
The telltale sign is a door that closes fine in the morning but refuses to close in the late afternoon, especially in the long, bright days of summer and the low-angle sun of fall and winter.
A few simple fixes can help:
- Close the door when the sun is not hitting the sensor directly, as a quick workaround.
- Ask a technician about swapping the sending and receiving units so the receiver sits on the shadier side.
- Have a pro add a small sun shield or hood over the receiving sensor.
Cleaning and Checking Alignment Yourself
These checks are safe for homeowners and often solve the problem in minutes. Unplug or disconnect power to the opener if you will be working near the door, and keep the door closed or fully open while you work.
- Clear the path. Look for anything near the sensors: trash bins, boxes, brooms, garden hoses, spider webs, or leaves.
- Clean the lenses. Gently wipe each sensor lens with a soft, dry microfiber cloth. Dust is a constant in our dry summers, and a thin film can be enough to weaken the beam.
- Check the brackets. Sensors are often bumped by cars, bikes, or feet. Make sure each bracket is firmly attached and both sensors sit at the same height.
- Aim them at each other. Gently adjust each sensor by hand so they point directly at one another. Watch the LEDs. When the receiving light goes steady, you are aligned.
- Tighten the wing nut or screw that holds each sensor so it stays in position.
Restore power and try closing the door. If it closes normally, you are done.
Test Auto-Reverse With a Roll of Paper Towels
Once the door closes, it is smart to confirm the safety system actually works. A roll of paper towels makes a great test object because it is soft and will not damage anything.
- Lay a roll of paper towels on its side on the floor in the center of the door opening, in line with the beam.
- Press the button to close the door.
- The door should stop and reverse before it reaches the roll. In many cases it will not even start closing.
You can also do a second test by letting the door close and waving the roll through the beam partway down. The door should reverse. If it does not reverse in either test, stop using the automatic opener and call a technician right away.
When the Problem Is Wiring or the Opener
If you have cleaned and aligned the sensors and the problem continues, the cause is likely deeper. Common culprits include:
- Damaged, chewed, or pinched low-voltage wires running from the sensors to the opener.
- Loose connections at the opener terminals.
- A failed sensor unit that needs replacement.
- A problem with the opener's logic board.
Never bypass or disconnect safety sensors to make a door work. A Braxdyne technician can test the wiring, replace sensors, and diagnose the opener for all major brands. We serve garage door repair in Sacramento, Elk Grove, Roseville, and many nearby cities.
We are open 7am to 9pm, seven days a week, with a free service call, a free estimate, and the price before we start. Every repair comes with a 90-day labor warranty and a 1-year parts warranty.
FAQ
Why does my garage door only fail to close in the afternoon?
That pattern almost always means sunlight is shining into the receiving sensor. Swapping the sensor positions or adding a sun shield usually fixes it.
Can I just remove the sensors?
No. Sensors are a critical safety feature that protects people and pets from a closing door. If they are not working, have them repaired instead of bypassed.
How often should I test the auto-reverse?
Testing once a month with a roll of paper towels is a simple habit that only takes a minute.
Sensor light still blinking? Call Braxdyne Garage Door Repair at (916) 848-5050 or text a photo of your sensors and opener, and we will help you sort it out. You can also book a repair online.