Years ago garage door openers were required to utilize safety sensors to prevent doors from closing on small children.
Garage door closes then opens liftmaster.
I hit the control agian and sometimes it will go back down and raise agian and read more.
These steps should fix most doors.
The opener s force setting may not be set correctly.
Chamberlain liftmaster professional 1 2 hp garage door opener that tends to open part way say 12 inches or so then stop.
Liftmaster uses the protector system which projects an invisible light beam across the door opening and automatically opens the door if something someone crosses it s path.
Make sure the small light on each sensor is lit and not flickering.
Never permit anyone to cross path of moving door.
Your travel down setting needs to be adjusted.
Always keep garage door in sight until completely closed.
The force setting tells the opener how much resistance the door should provide and if the opener detects more than is allowed the door will reverse.
Anytime the main light flashes 10 times and the door reverses to the open position it is a door sensor problem.
As is the case with so many issues at the home there s no one reason why your garage door closes then opens.
Close the garage door with the opener and watch it closely as it closes.
Now press the remote control.
This will cause the trolley to move into position and reconnect to the garage door.
Here s a rundown of some of the possible reasons this can be happening.
Try opening the garage door with the remote and see what happens.
Tweak them a bit.
To reconnect the garage door to your liftmaster garage door opener manually close the garage door pull the emergency release handle down.