The Cost of This Job
A single snapped cable on a torsion or extension system, with the drum and bottom bracket intact, is a contained job - new cable, check the drum for wear, re-tension, done. Where it gets expensive is when the cable took the drum, the bearing plate, or the track with it on the way down, which is common once a door's been running on a frayed cable for a while before it finally lets go. We don't have a flat number to quote you here without seeing the door, and we're not going to invent one - but the honest range depends heavily on whether this is one part or three. If your door is a double and only one cable went, expect us to recommend replacing both anyway; a cable old enough to fray on one side is old enough to fray on the other within months.
Can You Do This Yourself
Cable repair is one of the few garage door jobs where we'll tell you flatly not to try it on a torsion system. The cable is under direct load from a wound spring, and a cable job on torsion hardware means working next to that spring while it's under tension - that's how people lose fingers, not an exaggeration for the sake of one. On an extension-spring system, the stored energy is in the stretched springs themselves rather than a wound shaft, which makes it somewhat less violent if something slips, but you're still working with a door that weighs more than most people guess, held up by nothing once the second cable is loose. If you want to do something yourself, check: is the cable frayed at the drum end, is the bottom bracket bent, does the door sit level when both cables are slack. That tells you what you're dealing with before you call anyone, us included.
Where This Job Goes Sideways
The job goes sideways when the cable wasn't the first thing to fail. If a roller seized or a track bent out of alignment first, the cable that snapped afterward was reacting to that, not causing it - replace the cable alone and you're back out in a few months for the same call. It also goes sideways on doors where the opener kept trying to run the door after the cable let go; the opener's gears and the drive mechanism take a beating in those few seconds, and that's a separate conversation from the cable itself. We travel the 19 miles from San Ramon for these calls, so we'd rather diagnose the whole door on the first visit than make you wait on a second trip because we only looked at the part that broke loudest.
