Most garage door openers have an open and close limit control.
Garage door opener reopens after closing.
An exposed spot or a short circuit in the small gauge wire that leads from the garage door opener s motor unit to the control button on the wall may well cause your garage door to operate all on its own.
If not re engage it.
Replace broken chain belts sprockets or pulleys.
To troubleshoot the garage door opener button make sure it s clean and free of debris.
It goes partway down reverses direction and goes back up again.
Check to make sure the chain belt assembly is not broken or off its pulley.
They are usually on the motor housing and you access them by opening a panel or removing the housing cover.
You push the button to close the garage door.
If it closes before that distance has been traveled it thinks something is wrong and it reopens to help prevent any damage or safety risk.
If pushing the wall button and holding it does not make the door fully close then it is quite possible that your door is reversing itself because it is sensing undue resistance.
Check to make sure the pulley is not boken.
This will cause the door to open and close until the button becomes unstuck.
This is almost always the result of a dirty or obstructed safety feature.
Clean the button as well as the connections in the housing if this is the case.
This is a built in safety feature that is there in the event that something or someone gets in the way of the closing door.
Opener runs but the garage door does not move screw drive models make sure the carriage is engaged.
Close the garage door with the opener and watch it closely as it closes.
If the door stops short of closing lengthen the close limit by turning the control knob in the direction indicated usually counterclockwise.
The button can easily get dirty and stuck in the pushed position.
If the garage door does not close completely or begins to close and then opens back up again the down limit switch needs.
6 turn the up limit switch screw clockwise by one turn for every 3 inches that you need the garage door to raise up with a flat blade screwdriver.