How Does a Garage Door Sensor Work?

Understanding how a garage door opener safety sensor works can help you troubleshoot opener problems when the garage door reverses and returns to the full open position when you’re trying to close the garage door. Safety sensors mounted at the bottom of the garage door rails connect to the opener and indicate if a foreign object is blocking the door from closing properly.

In this article, we’ll describe how a garage door sensor works so you can effectively fix problems on your own and know when to call in professional garage door opener repair help.

How Does a Garage Door Sensor Work?

A garage door opener safety sensor includes these components:

• Emitter module.
• Receiver module.
• Wiring that connects the modules to the logic board in the garage door opener motor unit.

The emitter and receiver modules are connected to the rails of the garage door with brackets. They’re positioned about 6-inches above the ground to detect foreign objects or obstructions in the path of the closing garage door to prevent injuries or damage to the garage door.

The emitter gets power from the logic board and wires. It sends an infrared beam of light from the emitter to the receiver module. If the receiver module doesn’t detect the infrared beam because the beam is blocked by a person or object while closing the garage door, the opener will reverse the direction of the door and open it back up. The lights will typically blink (often 10 times) when the sensors detect an obstruction between the infrared beams.

The garage door opener will also reverse the door and blink the lights if the emitter and receiver modules are misaligned and the receiver module isn’t detecting the infrared beam from the emitter module.

How to Align Garage Door Opener Safety Sensor

Lights on the emitter and receiver modules help you align the safety sensors so they work properly.

The emitter module typically has a yellow light that should be lit all of the time. The receiver module has a green light that turns on when the receiver detects the emitted infrared beam because the modules are aligned and unblocked by any obstructions.

When aligning the sensors, make sure the yellow emitter light is on and adjust the positions of the emitter and receiver modules until the green light turns on – indicating that the infrared beam is aligned.

How to Tell When Something’s Wrong

The first key to knowing that something is wrong with the safety sensor is that the garage door won’t close using the opener. When you activate the garage door opener to shut the garage door, the door may begin to close and then reverse and move back to the fully open position. The lights on the garage door opener motor unit will often blink, indicating an obstruction in the safety sensor beam path or that the sensors aren’t aligned.

Remove the obstruction or realign the sensor in this situation.

If the door doesn’t move at all, the sensor may not be connected properly through the wires to the motor unit or the sensors may be defective. Wiring between the motor unit and the sensors or a bad logic board on the garage door opener could also be causing this failure.

Troubleshooting Garage Door Sensor Problems

To troubleshoot this garage door opener problem, follow the expert tips in this popular video from Sears PartsDirect that has over 1 million views:

If you’re unable to find and fix the garage door opener failure on your own, schedule garage door opener repair service and we’ll send a technician to your home to diagnose the issue and get your garage door opener working again.

Sometimes, you may encounter an intermittent problem with the garage door opener sensors – especially on clear winter days when sunlight reflects off snow and ice to interfere with the infrared sensing beams. When you suspect this type of problem is preventing the garage door from closing properly, install garage door opener sun shields as shown in this helpful video:

Maintaining Your Garage Door and Opener

Keeping your garage door and its opener well-maintained are key to their smooth operation. Problems with the door can jostle the safety sensors out of alignment or cause wiring problems. Checking the garage door opener regularly will ensure its safe operation.

Garage Door Maintenance

Here's a handy garage door maintenance checklist:

• Inspect and clean the garage door tracks: Begin by visually inspecting the tracks for signs of wear or damage. Clean any dirt or debris to ensure smooth operation and prevent the door from jamming.
• Lubricate moving parts: Use a silicone-based lubricant to reduce friction and ensure smooth operation of hinges, rollers, and springs. Wipe off any excess lubricant to prevent accumulation of dirt and debris.
• Check garage door springs: Garage door springs play a crucial role in balancing the door weight. Inspect them for signs of damage like rust or fraying. If you find any issues, it's best to seek professional help for spring adjustments or replacements.
• Inspect the garage door lock: Test the garage door lock operation. Lubricate parts if necessary. Replace any worn or broken parts. You’ll rarely use the garage door lock when you have a garage door opener installed, but you want to be sure it works if and when you do need it.

Garage Door Opener Maintenance

Here are essential tips to help keep your garage door opener well-maintained and working safely:

• Test the safety sensors: Ensure that safety features like sensors and the auto-reverse function are working correctly. You can test the safety sensors by placing an object in the door's path and ensuring the door reverses and goes back up when you activate the garage door opener to close the door. If these features are malfunctioning, troubleshoot the problem as discussed above or contact a garage door opener repair professional.
• Check the auto-reverse function: To test the auto-reverse safety function of your garage door opener, you can:
  • Make sure the garage door is fully open.
  • Place a 1.5 inch thick board or a 2x4 on the floor in the center of the garage door .
  • Press the remote or wall button to close the door.
  • The door should stop and reverse when it hits the board. If not, adjust the downforce setting as described below or have the garage door opener repaired or replaced by a professional.
• Check the garage door opener downforce setting: Some garage door openers use small dials on the motor unit to control the downforce when closing the garage door. Make sure that the downforce is not set too high. Excessive downforce is dangerous and can cause property damage or injury to anything caught in the path of door. Close the door with the opener and carefully grab it with your hand when the door is halfway down to make sure that the downforce isn't excessive. If you can stop the door using your hand, then no further adjustment is necessary. If you’re unable to stop the door with your hand, reduce the downforce in small increments. Make adjustments until the door closes completely on its own but will still stop if you catch it halfway down. Here’s a YouTube video that illustrates how to adjust force settings on common garage door openers:

If your garage door opener has a battery backup, test the battery. To test the battery, unplug the garage door opener; the battery status LED light should glow solid orange, indicating the opener is running on battery power. If the LED light flashes, that means it’s time to replace the battery because the battery power is low.

Maintenance and safety checks for your model of garage door opener may differ from the procedures described above. Check your owner’s manual for information about maintenance specific to your garage door opener.

Regular garage door maintenance not only extends your garage door's lifespan and keeps it operating safely, but also helps avoid unexpected breakdowns.