What can I do if the garage door won't close after tightening the safety sensor mount?

expert EXPERT January 08, 2008

If the door reverses open and flashes the lights (unless you hold the button down continuously) then the problem is still likely to be with the safety sensors.

There are two possibilities that come to mind. First, when the sensor was loose the wiring might have been damaged and finally failed when you were adjusting the sensor mount, or second, the sensors are still not aligned properly.

In either case, you can confirm whether the sensors are working by checking the LED lights on them. One side will be lit, normally with an orange or red looking light, at all times to indicate that power is getting to the sensors. The other sensor should normally have a green LED lit. If there is no light on one of the sensors, or if the light on one of them flickers or flashes, it indicates the sensors are not properly in line and still need adjusting.

As the sensors are adjusted more in-line with each other, and begin to "see" each other better, the dim or flickering LED will become brighter and more constant. Once the sensors are properly aligned there should be a solid visible LED on each.

If the sensors seem to be aligned but the door sill will not close normally there could be a problem with sunlight going directly into one of the sensor "eyes." You can try blocking any sunlight to test if that is an issue but to confirm any further sensor problems you will probably need to remove the sensors from their mounts and physically put them face to face.

Testing the sensors face-to face is not simple since they seldom have enough room to reach to each other. Often it is simpler to cut the wires a few inches from each sensor and then attach the sensors directly to the overhead logic board rather than it is to remove a bunch of wiring from the walls in order to get them enough together. Just be sure to leave enough wire length for you to be able to reattach the sensors once you determine find and fix any problem.

Cutting the wires also allows you to bypass all the wiring going from the overhead unit to the garage door, which can be problem area if the staples are tight enough to have pinched or worked through the coating on the wires. If hooking the sensors directly to the overhead logic board and holding them eye-to-eye suddenly allows the door to work then there was likely a wiring problem.