Garage door sensors perform a pivotal role in preventing injury to persons and damage to property. The sensors mount at the entrance to the garage, near the floor, on opposite sides of the garage door frame. An infrared beam transmits between the two sensors. If the beam is obstructed by an object of some type, the garage door senses the obstruction and prevents the door from closing. Sometimes, these sensors can malfunction, causing the garage door to think something is in the door's path when nothing is.
Check the plug for the garage door opener and ensure it is securely plugged into the outlet. The plug can work itself loose over time and prevent the door from opening or closing.
Look at the light emitting diodes (LED) on each of the two sensors. When the infrared beam is transmitting from one of the sensors, and received at the second sensor, each will have a green LED lit. If one or both of the sensors displays a red or blinking red LED light, that particular sensor has a problem.
Clean the lenses on both sensors with a soft tissue so they properly send and receive the infrared beam of light.
Adjust the two sensors where they point directly at one another. While the sensors do have a relatively wide tolerance for misalignment, if the two sensors are not aligned, they will not work properly.
Inspect the terminal connection at the garage door opener where the sensors connect to the opener. A strip of screws under the front face of the garage door opener is where the sensor wires land to the terminal. A loose or corroded connection at the terminal screw prevents the sensors from transmitting the appropriate signal back to the opener.
Replace the garage door sensors if cleaning, adjustment or inspection of the terminal leads fails to solve the problem.