Every garage door has two cables — one on each side — that transfer the spring's stored energy to the door itself. When they fail, the door drops.
How they work
The cable wraps around a drum at the top corner of the door and connects to the bottom bracket at the bottom corner.
Why they fail here
Salt air corrodes the strands. A broken spring whipping loose can shred a cable in one shot. Wear on the drum can nick the cable.
The repair
Always replaced in pairs. Drums re-set to identical wrap counts. Door rebalanced afterward.
