How to tell if a garage door spring is bad?

You can tell if a garage door spring is bad by observing physical signs, door behavior, and sounds that indicate spring wear or breakage, as springs are critical for counterbalancing door weight. The most obvious sign of bad or broken torsion spring is visible gap in coil, as spring mounted above door should be continuous coil, and if you see 2 to 4 inch gap where coil separated, spring broken and needs immediate replacement. Door that is very heavy to lift manually after pulling emergency release cord indicates spring bad or broken, as good springs should allow door to lift easily with one hand and stay halfway open when balanced; if door falls or won't stay, spring weak. Door that opens only few inches then stops or opener hums but doesn't lift door indicates spring cannot counterbalance weight and opener overloads. Loud bang from garage when spring breaks is classic sign, often heard when door not moving. Door that is crooked or opens unevenly suggests one of two springs broken or extension spring on one side broken. Rust, pitting, or stretched coils on spring indicate wear and imminent failure. Extension springs that are stretched out and don't contract indicate bad. Opener that struggles, makes loud noise, or reverses indicates spring issue causing extra strain. If spring is 7 to 10 years old and has 10,000 cycles, it is near end of life and should be inspected. Call professional if you suspect bad spring, as springs under high tension dangerous.