These sensors are generally mounted no more than six inches off the ground, and to each rail of the garage door. One device shoots an invisible beam that directly points into the optical receiver of the one at the opposite side of the opening. The photo sensor prevents the door from crushing things or damaging the door by contacting items in its pathway.
Problems with the photo sensor may occur as a result of the sensor being bumped, from vibration causing the sensor to shift after numerous openings and closings, a dirty sensor, burnt out from pressure washing the garage floor, or because the sensor is being hit by direct sunlight.
These sensors must stay in direct alignment in order for the garage door opener to function correctly. This is the most likely cause for a garage door not closing properly. First, check to see if your sensors have LED lights. These lights activate when the sensors are functioning correctly. If one light is out or is blinking, then that may be an indication the sensors are not properly aligned. Attempt to adjust the sensors in all directions until both LED lights activate. If you have trouble drawing an imaginary line then you can use string, level and a tape measure to insure they are perfectly level. Once you have solid LED lights, insure the sensor lenses are clean and then you can activate the garage doors.
If adjusting the sensors does not solve your problem, this may be an indication that the wiring needs to be repaired or the sensor is broken and in need of being replaced. One last thing, if the malfunctions are at a certain time of the day and during certain seasons of the year, then it may be due to the sun directing light into one of the sensors. There are shades that can be attached to the sensor to prevent the light from directly hitting the sensor lens. As always, simple regular maintenance around your home can alleviate headaches and save you money in the long run.
For more on this or other home care subjects, contact Scott at www.scottsauer.com.