There are two types of garage door sensor problems. The first occurs with remote devices -- the handheld garage remotes that are kept in cars to open the door at a distance. In this case, problems are generally caused by either faulty sensors or problems with the signal code. The second type of problem concerns the wired connection inside the garage itself, used to close or open the door from inside. In this case, the problem could be caused by faulty wiring or how the door's movements are programmed.
Most garage remotes use an infrared or radio-based system to communicate with garage door sensors. The remotes send a coded signal through the air that is picked up by the sensors, which then give the garage door a signal to move. Separate sensors detect whether the door is open or closed. If open, the sensors tell the door to close, and vice versa. There are also safety features that will automatically pause or reverse the garage door movement.
While radio wave signals can be picked up by remote systems without much interference, infrared signals need some sort of line-of-sight connection to work properly. An infrared sensor problem can usually be identified by switching between the wired, in-garage button and the remote button. If the garage door works properly with the wired connection but not the remote transmitter, the problem is probably signal-related. Most sensors have a small red light that will blink where the signal is sent/picked up, known as the "eye." Sometimes sensors only need to be cleaned or readjusted to resume working properly.
Garage doors come with programmed limits that tell the door how far to move down. If these parameters are wrong, based on how tall the garage opening is, the door will not close properly. It will either leave a gap between the lip of the door and the ground, or collide with the cement and automatically retract. These problems can be solved by making sure the garage door is properly aligned with the height of the garage.
Garage doors are equipped with photoelectric sensors near the base of the door opening that ensure the door will not close down on anything. When an object interrupts the lightwave-based connection, the door will either refuse to close or automatically freeze. If these safety sensors are misaligned or blocked in some way, the door will not function properly.
Before adjusting how the garage door functions, users should always make sure the problem doesn't stem from a more simple problem. Many problems with transmitters are caused by low batteries, or an uncoded signal. Sometimes objects can be placed in front of sensors so the signal cannot reach its destination. Batteries and signal pathways should be examined before moving on to more serious causes.