Problem
Garage door reverses or won't close
A door that goes down and comes back up usually thinks something is in its way. Start with the sensors near the floor.
Say the town and what the door is doing.
Check the sensors
Most homes have a pair, one on each side of the door. The Consumer Product Safety Commission says they should sit 4 to 6 inches above the floor. Each usually has a small light, and a blinking or dark light usually means the pair can't see each other.
Wipe the lenses. Move anything in the beam, such as a shovel or snow pushed in from outside. Look for a bump that has turned one sensor away from the other.
If the sensors look fine
The door may be meeting something early, such as a bent bottom edge or ice on the floor. If it closes by hand but not with the opener, the opener's settings are the likely cause.
What to leave to a contractor
Don't change the limit or force settings on a door that also feels heavy or sticks. A wrong setting can stop the safety reverse from working.
Springs and cables hold enough force to badly hurt someone. Don't adjust, unwind or replace them yourself. If one is broken, leave it alone and stay clear of the door.
The opener repair page lists other causes.
Call about your door
Say the town and what the door is doing. You will be connected with an independent garage door contractor.