Like mentioned above there are two lenses one on each side.
Garage door chain working but will not close.
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.
Another thing that can prevent your garage door from closing are obstructions that are blocking the lenses.
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.
If something is blocking the safety beam then the garage door will not close.
The motor will run but will not move the chain.
When the cord is pulled the motor is disengaged from the chain.
Depending on the 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.
In most cases the cause will be a stripped gear or a chain that has come off the sprocket.
There s something wrong with the garage door opener that s stopping it from opening the door for you.
Most garage doors have an emergency release typically a red pull cord that allows the door to be opened and closed manually.
Press the remote or the wall mounted start switch listen to the motor and watch the movement of the chain.
If this is the case the motor will run but as the chain isn t where it should be it can t generate the lift to open the door.
If your garage door won t close all the way the problem could be due to a blocked photo eye.
If the motor hums but the chain doesn t move that indicates a problem with the motor.