How Do I Know If My Garage Door Sensor Is Bad? 7 Signs to Check Immediately

If you have a garage door refusing to close or acting strangely, your first thought is usually the springs or the garage door opener. But very often, the problem starts with a small part near the floor: the sensor.

Your automatic garage door has two sensors on either side, near the bottom of the garage door frame. 

These are part of the safety features that can prevent the door from closing on a person, pet, or your car. When these sensors go bad or get misaligned, your door will not close, or it will behave like it has a mind of its own.

Below, we will walk through how garage door sensors work, the most common signs of sensor issues, simple troubleshooting steps, and when it is time to replace the sensors or call a professional garage door technician in The Woodlands, Texas.

How Garage Door Sensors Work & Why They Matter

Modern garage door sensors play a critical safety role. They sit on the sides of the garage door, a few inches off the floor, attached to a mounting bracket on each side of the door.

Here is how these door sensors work:

• There are two sensors:

• One sensor sends an infrared beam across the garage doorway.
• The receiving sensor picks up that beam on the opposite side of the door.

• If something is directly in the path of that beam, the sensors prevent the door from closing.
• If the beam is blocked, misaligned, or there is sensor failure, the opener will stop or reverse the door opening or closing to prevent the door from closing on anything.

These safety eyes are an important safety feature in any automatic garage door system. When the sensors work correctly, they help prevent injuries and damage. When they malfunction, they can prevent the door from closing at all.

7 Common Signs Your Garage Door Sensor Is Bad

If you are wondering “How do I know if my garage door sensor is bad?”, start with these signs. Any of these problems with your garage door can point to sensor issues.

1. The door will not close or won’t close unless you hold the button

If your garage door refuses to close from the wall button or remote, but it will close the garage door only when you hold down the wall button continuously, your safety sensor may be the issue.

Most openers, including LiftMaster and similar brands, are designed so that holding the button down overrides the safety mechanism. When you have to do this, it is a clear warning that the sensor is not working properly.

2. Door closes normally sometimes, then suddenly reverses

If the door closes normally on one try and then suddenly reverses halfway the next time, that inconsistency points to a possible sensor malfunction or misalignment.

The sensors could be:

• Slightly misaligned
• Intermittently blocked by debris or a spider web
• Experiencing loose sensor wires or wiring problems

This kind of intermittent malfunctioning garage door behavior is very common when sensors start to fail.

3. Flashing lights or unusual LED lights on the sensor

Each sensor has small LED lights that tell you if the sensor is working or not:

• One sensor usually has a steady light when it is powered.
• The receiving sensor should have a solid light when the infrared beam is lined up.
  

If one sensor is dark, flickering, or a light is blinking, the sensor may have:

• Misalignment
• Wiring issues
• Internal sensor failure

Pay close attention to what the lights are doing, as they often point directly to the problem.

4. The sensor lenses look dirty or foggy

Your sensor lenses sit near the floor, so they collect:

• Dust and dirt
• Grass clippings
• Debris and weather-related grime
• Spider web buildup
  

If the lenses are dirty, the sensors could interpret that as something blocking the infrared beam.

That will prevent the door from closing properly and can make it look like the sensors go bad, even if they are fine.

5. Sensors are obviously misaligned or loose on the bracket

If you look at the sensors on either side of the garage door and notice:

• One sensor is pointing slightly up or down
• The mounting bracket feels loose
• A screw is missing or the bracket is bent

Then alignment issues are very likely. Even a small misalignment can prevent the safety sensor from seeing the infrared beam.

In this case the sensor is still probably good, but it needs to be aligned correctly so the sensors work as designed.

6. Sunlight interference at certain times of day

Direct sunlight can interfere with the infrared beam on some garage door systems. If you notice the door doesn’t close the garage at a specific time of day when the sun hits one side of the door, that is a clue.

In those cases:

• The sunlight can trick the receiving sensor.
• The opener thinks something is in the way, so it will prevent the door from closing.

You can sometimes install a sun shield to help keep the sensors working despite the sun.

7. Visible damage to the sensors or wiring

If there is clear damage to the sensors or sensor wires, such as:

• Cracked plastic on the sensor housing
• Exposed electrical wiring
• A bent bracket on the side of the door
• Wires pulled loose from the back of the sensors

Then it is likely time to replace the sensors and possibly address wiring problems in the garage door system.

This type of damage to the sensors can happen from kids, pets, tools, or even a car tire hitting the sensor.

Simple Troubleshooting Steps Before You Call a Professional

Before you assume you need garage door sensor replacement, you can start troubleshooting with a few safe, simple steps.

Start troubleshooting your garage door with a safety check

1. Unplug the opener to cut electricity to the system.
2. Open the garage door and secure it, or use the release to move the door manually.
3. Make sure no kids or pets are directly in the path of the door.

Safety first. Sensors play an important role, so never bypass them permanently.

Step 1: Clean the sensor lenses

Use a soft, dry cloth to gently wipe away dust or debris:

• Wipe each lens carefully.
• Remove any spider web or loose debris around the lens and bracket.
• Check for mud, dirt, or moisture spots.

Sometimes this quick fix is all it takes to fix your garage door if the sensor was simply dirty.

Step 2: Check for obstructions near the sensors

Look around the sensors on either side of your door:

• Are there leaves, toys, tools, or boxes near the sensors?
• Is anything sitting directly in the path of the infrared beam?

Even a slender object can prevent the door from closing properly, because the safety feature is designed to prevent the door from closing on anything.

Clear the garage doorway so nothing can block the beam.

Step 3: Inspect wiring and sensor wires

Now look at the wiring closely:

• Make sure sensor wires are not frayed, cut, or pinched.
• Check that each wire is firmly connected at the sensor and at the opener.
• Look for obvious wiring problems, such as loose connections or bare copper.

If you notice damaged electrical wiring, it is usually best to call a professional, since working with electricity is risky without proper training.

Step 4: Check alignment and adjust the sensors

If the sensors still are not working properly, you may have misaligned sensors.

Simple steps to align:

1. Loosen the wing nut that holds each sensor to the mounting bracket.
2. Gently move one sensor until it is level and pointed directly at the sensor on the opposite side of the door.
3. Tighten the wing nut with your fingers or a screwdriver, being careful not to overtighten the screw.
4. Repeat on the other side of the door.

Some people run a string across the two sensors to help line them up. When the LED lights show a steady light on the receiving sensor, the alignment issues are usually resolved.

Step 5: Test the system

After cleaning and aligning:

1. Plug the opener back in.
2. Use the wall button or remote to close the garage door.
3. If the door closes normally, your sensor is working and you are done.
4. If the door still won’t close or the door will not close consistently, the sensor may be failing internally.

At this point, it might be time to replace the sensors or schedule door service.

When It Is Time to Replace the Sensors or Call a Professional

If you have tried simple troubleshooting steps and the sensors still are not working, here are some signs it is time to replace the sensors or call a professional:

• One sensor light will not come on at all, even after cleaning and aligning.
• The door doesn’t respond consistently, and there are no visible obstructions.
• There is clear damage to the sensor, bracket, or wiring.
• You suspect sensor failure inside the unit.

Sometimes you can remove the sensors and install new ones yourself, but many homeowners in The Woodlands prefer a skilled garage door technician to:

• Fix your garage door safely
• Handle any wiring issues properly
• Match the right sensor to your specific opener model
• Confirm the entire garage door system is working properly

If you are already seeing issues with your garage door opener itself, it might be a good time to ask about complete garage door opener repair and installation instead of only replacing sensors.

Protect Your Home With Reliable Garage Door Sensors

Door sensors play an important role in keeping your family, pets, and vehicles safe. When they are working properly, they are an important safety feature that prevents accidents. When they malfunction, they can prevent the door from closing or cause your garage door’s safety mechanism to react when nothing is there.

If you notice your door will not close, the door opening and then reversing, strange flashing lights, or any other issues with your garage door, do not ignore them. Start troubleshooting your garage door with the simple steps above. Clean the lenses, check alignment, and look for damage.

If the sensor is still giving you trouble, it may be time to replace the sensors or schedule professional door service in The Woodlands. A trained technician can quickly diagnose sensor issues, handle any damage to the sensors or wiring, and make sure your new garage door or existing door is safe and reliable.

If your door still won’t close after basic checks, call a professional and let an expert take it from there.