Of all the parts on a garage door, the springs are the ones you should never try to fix yourself. They are also one of the most common failures. Understanding why they are dangerous, and how to spot a break, will keep you safe and help you act quickly.
Why springs are so dangerous Garage door springs are under enormous tension, storing the energy needed to lift a door that can weigh well over 100 pounds. When a spring is wound or fails, that stored force can release suddenly and violently. Every year, do-it-yourselfers suffer serious hand, face, and eye injuries trying to replace them. This is not a job for borrowed tools and a YouTube video.
How to spot a broken spring - A loud bang from the garage, often heard even from inside the house. - The door will not open, or the opener strains and stops. - The door feels extremely heavy if you try the manual release. - A visible gap in the coil of the spring above the door. - The door opens a few inches then stops or slams down.
If you see a gap in the spring, stop using the door entirely.