How do I know if my Garage Door Sensor is Bad?

Although automated garage doors grace us with undeniable convenience, they pose inherent dangers to garage users. The primary function of safety sensors is to prevent unforeseen accidents resulting from automatic garage doors. Unfortunately, just like most systems, automated garage doors are prone to malfunctioning, resulting from defective sensors. Without functional safety sensors, an automatic garage door system is incomplete. That said, the importance of ensuring your safety sensors are functional cannot be emphasized enough, and that poses the question; how do I know if my garage door sensor is bad?

You can know if your garage door sensor is bad by simply putting it to test. You could do this by placing a random object, preferably not less than six inches high, beneath your garage door then signal it to close. A functional garage door sensor should prevent the closure of the garage door with an object underneath. On the contrary, if your garage door sensor is defective, expect the garage door to close and end up damaging the object. Alternatively, failure of the garage door to close even in the absence of an object underneath also signifies that your sensors are defective.

How Garage Door Sensors Work

Among the components of an automated garage door system are garage door openers and safety sensors. Although garage door openers can operate even in the absence of sensors, the latter is a requisite for the safety of garage users.

Most contemporary garage doors are remote-operated to maximize convenience. Thanks to this technology, you can operate your garage door from the comfort of your car. For safety purposes, remote-controlled garage systems incorporate the use of infrared signals.

Once you prompt your garage door to open or close using the remote, the infrared signals activate the electric motor, which facilitates the action. Garage door safety sensors comprise an infrared light emitter and receiver.

The emitter and receiver are termed as photo eyes and are placed opposite to each other, approximately six inches from the ground. In between the sensors is a laser beam that must be uninterrupted for the garage door to close. Unfortunately, an object beneath the garage door obstructs this laser beam, preventing the closure of the garage door and forcing it to retract.

Therefore, you may wonder why your garage door won’t close even in the absence of an object underneath or why it won’t retract in the presence of an object. Unfortunately, as fascinating as garage door sensor technology may be, it is bound to fail at some point, and you are faced with the responsibility of promptly addressing the problem.

Identifying Garage Door Sensor Problems

Once your garage door sensor fails the test, you may begin scratching your head for the cause of the problem. Based on how garage door sensors work, we can deduce that the most probable cause is obstruction, but by what? Here are the most common garage door sensor problems:


The garage houses old tools, books, spiders, and whatnots. It is, therefore, no wonder that the lenses on your garage door sensor could be covered by dust or cobwebs that end up obstructing the laser beam. Even the tiniest of debris could obstruct the beam, preventing the sensors from communicating.

Consequently, you could look out for other substances such as old brooms that could be standing in the way of the garage door safety sensors.


The prevailing weather is yet another common cause of defective garage door sensors. It often becomes a problem during bad weather when you fail to close the garage door, thus allowing moisture into the garage. In this way, the garage door sensors tend to be clogged up with moisture, preventing them from functioning correctly.

Alternatively, bad weather could result in damaged or loose wires, leaving the garage door sensors defective. Sunlight could also prevent the sensors from functioning correctly by reflecting light on the lenses, thus interfering with the beam.


Garage door sensors have to be in line with each other for them to function effectively. Unfortunately, misalignment of sensors is quite common, especially for garage doors with many users. It could be due to kids or pets accidentally hitting the sensors or vibrations from the surrounding.

Fortunately, most garage door sensors are fitted with LED lights to help in detecting this problem. A properly functional garage door sensor should display steady green lights. If you see red blinking LED lights on either of the sensors, then your sensors could not be adequately aligned.

However, some garage door sensors do not feature indicator lights. In such cases, it is ideal to visually inspect the sensors to gauge whether they are in line or measure their heights using tape.

Power Supply

Lack of power supply could also be one reason why your garage door sensor is not functioning. This factor should probably be the first to look out for before plunging into other ideas. First, consider checking whether you have plugged in or switched on the power supply.

For battery-powered garage doors, consider checking if the batteries are depleted or if they are still functional.

How to Solve Garage Door Sensor Problems

Most garage door sensor problems have DIY solutions. After identifying the problem, you may want to find a way to resolve it yourself to save on costs. Depending on the situation at hand, below are some of the ways to solve garage door sensor problems:

Ensure the Sensors are On

You may want to ensure the power supply is plugged in before checking for other faults and ending up causing unnecessary damage. Additionally, look out for faulty wires that could limit the power supply to the garage door system. In this case, you may be obliged to replace or tighten the wires. Also, consider recharging or replacing the batteries in the case of battery-powered garage doors.

Clean the Lenses

If your sensors are covered with debris, then this is the way to go. In such instances, consider wiping away any form of dirt that could be obstructing the infrared beam of light. Then, run a soft dry piece of cloth or towel over the lenses for best results. 

Using a wet cloth could end up covering the lenses with moisture. If you use a wet cloth to remove tough debris, consider wiping the lenses again using a dry cloth while ensuring you do not scratch the lens in the process.

Align the sensors

Here, you may have to get a bit practical to achieve the desired results. First, you will need a screwdriver to loosen the nuts on the sensors. Once they are loose, adjusting them should be a breeze. Adjust them until you see the LED lights glowing steadily instead of blinking, then fasten the nuts. Steady LED lights indicate that the sensors are functional, and your garage door should close normally.

Seek Professional Help

If all your efforts prove futile, you might have to hire an expert to do the job. Consequently, seeking professional help is the ideal solution if there is a problem with the wiring. Such a problem may present a significant safety hazard, which should be controlled as soon as possible.

Ensure you provide all the relevant information to the repair professionals. The information should include the problems you may have identified to give them a rough idea of how to go about the situation.


The functionality of garage door sensors should be a significant concern for anyone who owns an automatic garage door system. Accidents caused by these systems could be costly or even fatal, making garage door sensors a mandatory safety requirement. In addition, these systems are bound to malfunction and should therefore be inspected time and again.

A malfunctioning garage door sensor fails to retract the garage door despite the presence of an obstructing object. Flickering indicator lights on your garage door sensor could be the answer to why your garage door opens effortlessly but fails to close or closes partially. In case of such occurrences, be sure to take action as soon as possible as it is better to be safe than sorry.

Other Related Articles