How to fix a loose garage door cable?

To fix a loose garage door cable that has slack, has come off the drum, or is not winding properly, you must exercise extreme caution because cables are under high tension from springs, and this repair is best left to professionals. If the cable is loose due to a broken spring, the spring must be replaced first, as the spring provides tension to keep cables tight around drums; do not attempt to tighten cables with broken spring. If the spring is intact but cable came off the drum, often because the door was opened manually with opener disconnected or hit an obstruction, you need to fully close the door and clamp it with locking pliers or clamps on tracks above rollers to prevent it from moving. Then, using winding bars for torsion systems, you must carefully unwind spring tension, reseat the cable into the groove of the drum and around bottom bracket, ensuring it is not twisted, and then rewind spring with proper number of quarter turns. For extension spring systems, you must open door fully, clamp it, and relieve tension by disconnecting springs. Never attempt to fix loose cable with door open and springs under tension, as cable can snap and cause injury. The cable must be properly seated in drum grooves and have equal tension both sides to keep door balanced. If cable is frayed or kinked, replace it with new aircraft-grade cable costing 15 to 40 dollars. Professional cable repair costs 100 to 250 dollars including service.