If your garage door refuses to move in the down direction, it may be caused by an issue with safety reversing sensors. The sensors are safety devices preventing the garage door from closing on people or animals.
When sensors are not connected or aligned correctly, or something is blocking them, the door won’t close. As a temporary solution, you can close the door manually by pressing and holding the wall button.
Cleaning and aligning
Do you notice a red or blinking light on the sensor? If yes, then start by cleaning the electric-eye lenses from any debris, dust or cobwebs. Test the door. Does it close completely without hesitation? If no, then you need to adjust the sensors.
Ensure that the sensors are pointing at each other. Use an adjustable wrench to loosen the nuts holding each sensor to the L-brackets. Now you can move each sensor a little by hand so that the red or green lights are lit. Do you see this result? These lights show that the lenses are aligned correctly. Tighten the nuts.
Test the door. Has the problem disappeared? If the door still does not close properly, you need to troubleshoot the electrical circuit.
The sensors are connected to the garage door opener with the help of low voltage wiring. If the green or red power-indicator lights on the sensors are not illuminated, you need to check the wiring.
Disconnect the power cord from the outlet at the ceiling (you will have to use a stepladder). Find the place where the ends of the wires attach and reattach a loose wire to the appropriate connection terminal. Use a screwdriver to tighten the terminal screw.
Now it’s time to plug in the power cord and check whether the power-indicator lights appeared. If no, it is a good idea to ensure there are no worn wires. If you notice any damage, replace the broken or bare wire. To do this, loosen the terminal screws connected to the broken wires, pull the wires out and disconnect them. Strip 1/2 inch of insulation off the end of the replacement wires. Connect the ends to the terminals on the sensor, thread the wires through the fasteners, strip the ends, and connect the wires to the terminals. Now you can tighten the screw and plug in the opener.
Replacing the sensors
If you cannot resolve the issue in this way, you will probably have to replace one or both sensors. To purchase the right sensors, check out the make and model number of your opener. You may open and close your door manually while waiting for the replacement sensors.