Garage Door Won’t Close All the Way
If the garage door opens correctly but fails to close completely, there may be one of three common causes:
The close-limit switch may need adjusting. Your garage door has set-limit switches that instruct the motor when to stop running—both when it is opening, and when it is closing. If the close-limit switch is set wrong, it may prevent the door from closing It can also cause the opener to reverse or pull back up when you attempt to close it.
The close-limit switch is a safety measure that keeps people from being hit and having the door close on them—it is a necessary and required device for all garage door openers. Adjusting the limit switch will stop your garage door from behaving erratically.
Different garage doors have different means of adjusting the set-limit switches, but it is usually a screw feature on the motor unit that is turned to adjust how far the door descends.
The safety sensors may need adjustment or realignment. Near the bottom of the door track on both sides are electronic eyes that require a clear line of view between them. If the sightlines are clear between the eyes, the door will close smoothly all the way to the floor. However, if anything is blocking the sightline, or if the brackets holding the electronic eyes are out of alignment, the door will fail to descend all the way. In most cases, the door will stop or reverse, and lights will flash to tell you there is a problem.
Make sure there is nothing blocking the sight path between the electronic sensors. Sometimes, leaves or debris can block the sensors; it if happens frequently, it might be that vibrations from the door in the tracks are loosening the brackets holding the sensors and must be realigned.
Less frequently, rusted or damaged rollers can cause the door to bind in the tracks. Replacing damaged rollers or lubricating them with silicone lubricant can correct this problem. Sometimes the tracks themselves may shift or get bent, which can also cause the problem.
Source: The Spruce