Push your garage door opener wall button or a remote control to close the garage door.
Roll a large ball slowly through the garage door opening while the door is closing. The ball will break the infrared beam. The door should stop momentarily, and then reverse direction. If the door does not stop and reverse, the photo eye sensors need adjusting.
Clean off the sensors with a dry cloth. Look for the LED lights on each sensor. Both lights should be illuminating. If one is not lit, adjust the sensors to line up with each other.
Loosen the securing screw on the unlit sensor with a wrench. Move the sensor up and down until the LED lights and stays lit. Hold the sensor in position, and tighten the securing nut.
Push the wall button station to open the garage door. Close the door again and roll the ball through the door opening. If the sensors fail the test again, call a service professional to inspect the system.