Probably the most common phone call we get in the service department is “My garage door keeps reversing and I can’t get it to close” or “My remotes won’t close the door and I have to hold the wall button until the door is all the way down for it to stay closed.” Usually this is a sure sign that there is an issue with the garage door’s photo eye system.
In 1993 a law was passed in the U.S. requiring garage door operators to be equipped with a secondary reversing system, which most operators have in the form of photo eyes. Photo eyes (or safety sensors) are mounted to the track on either side of the garage door about 6 inches up from the ground. The photo eyes send an infrared beam across the bottom of your garage door opening, if that beam is broken, the door will reverse. This is a safety feature that has been added to garage door openers to help prevent the door from closing on a car, pet, or even a child.
If you are finding that your door is reversing for no apparent reason, here are a couple things that you can check to see if the issue has to do with the photo eyes.
After following these tips, if you are still having problems getting the door to close and you need to leave your house, you can override the sensors by holding down the wall button until the door is all the way down or you can put your door on manual by disconnecting it from the operator. Then, call your local D & D GARAGE DOORS professional and schedule an appointment for them to come and check out the situation and see if there may be other issues involved.
Sources sited: http://en.wikipedia.org/wiki/Garage_door_opener