There is one on each side of the door.
Garage door goes up but not down.
Safety sensors if the door goes up but you can t make it go down you probably need to adjust the sensors.
They both have lights and both lights should be.
If your garage door hits it bounces up and starts to open again your garage door is working well.
However if your garage door doesn t bounce back up then you know you have a problem.
It goes partway down reverses direction and goes back up again.
If you find that your garage door closes part way and then goes back up this can be triggered by objects on the ground blocking their path such as garbage cans or toys.
This is almost always the result of a dirty or obstructed safety feature.
This could include small items like rocks gum or mud buildup.
Turn off the sure lock aka vacation mode on the wall console check if limits are properly set check the door balance condition and door spring check opening force control or force settings.
To fix this issue increase the down limit one quarter turn.