When the opener is activated the screw rotates causing the nut to move until it reaches the switch.
Garage door opener starts then reverses.
It goes partway down reverses direction and goes back up again.
Photo eyes or safety sensors are mounted to the track on either side of the garage door about 6 inches up from the ground.
One for the opening limit and one for the closing limit.
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 almost always the result of a dirty.
Reverses on its own.
When the opener reverses the screw turns the opposite way and the nut travels back.
However if the door travels all the way closed and then reverses look to the 2 nd 3 rd possible causes.
There may be two nuts on one track.
This happens from both the read more.
I have a garage door opener stanley d1000 a07 date 98523 i hit the wall button or remote button and it hums starts to move then stops and reverses itself then stops.