A loud bang from the garage
The classic one. People describe it as a gunshot or something heavy falling. That is a torsion spring releasing all its stored energy at once. The door may still look fine.
A visible gap in the coiled spring
Look at the spring on the bar above the door. A healthy torsion spring is a continuous tight coil. A broken one has a clear two- to three-inch gap where it separated.
The door lifts a few inches then stops
The opener's safety system senses the load is far heavier than expected and gives up. That is the opener protecting itself, and it is a good thing.
The door slams shut instead of settling
Without spring counterbalance, the door is simply heavy. If it drops fast when closing, treat the opening as dangerous until it is fixed.
The door is crooked in the opening
On extension-spring doors, one spring failing lifts one side higher than the other. This also jams the door in the track and can bend the rails.
The top section is bending or flexing
An opener pulling against a dead spring puts all that force into the top panel. Keep running it and you turn a spring repair into a panel repair.
Cables hanging loose
When tension disappears, cables unspool from the drums and hang slack. Once they have jumped the drum they need to be re-spooled properly, not just pulled tight.
When to hand it over
If any of this points at springs, cables or a door that has gone out of balance, that is the point to stop. Supreme Garage Doors Repair Services covers garage door spring repair and every other garage door service across New Hampshire, with same-day slots most days and a line answered 24 hours at (888) 904-6236.