One sends a beam of infra red light to the other.
Garage door not closing without holding button down.
You will find that the door will only move an inch or so in the close direction and reverse.
If something is blocking the safety beam then the garage door will not close.
In order to fix this you ll want to make small changes to the close limit setting until the door opener knows to stop once the door has reached the floor.
First check the sensor lights.
The transmitters remotes will not work to close the garage door.
When you can close the door with the wall button by holding it down until it completely closes and the remotes only make the door move a small amount and the door returns that is the sign of the safety sensor system.
They can easily become mis aligned due to bumping twisting and loose mounting.
If an operational problem exists and the garage door opener will not close the opener can be forced to close.
Another thing that can prevent your garage door from closing are obstructions that are blocking the lenses.
If your garage door is closing fully and then reversing to open again then it may be due to a problem with the close limit switch.
Like mentioned above there are two lenses one on each side.
Door starts down then stops before it is closed.
When this happens your garage door will only close by holding down on the wall button or wall console until the door fully closes.
Check for interference from adjacent photo eye sensors of any brand.
Clutter or obstructions that block the sensor are the first problems to look for if your door won t close or in extreme cases open at all.
Press and hold the wall console button until the garage door is completey closed.