Things You'll Need
Phillips head screwdriver
Replacement garage door chain
A broken garage door chain will immediately impact your garage door's operation and render its automatic, motorized capability effectively useless. Immediate troubleshooting is required, and a new garage door chain will need to be installed in place of the old one. This requires the activation of the door's emergency release feature and the manipulation of the tension bolt on both the existing and replacement garage door chains. You can fix your broken door chain, regardless of your familiarity with garage door repairs.
Locate the garage door's emergency release rope. This is a yellow or red rope that hangs from the overhead garage door assembly. Pull this rope down. This will disengage the door's slide and ensure that the door cannot be operated automatically via the garage door opener. This effectively sets the door into manual operation mode.
Begin the chain disassembly. The chain is located in the garage door's pulley bar. This distinctive chain features a tension bolt with a nut at its open end. Remove this nut from the bolt with a socket wrench.
Remove the screw from the slot beneath the bolt with a Phillips head screwdriver. You can simply pull the chain out of the pulley bar by hand once the screw has been removed.
Stretch the new chain out on the ground and ensure that the tension bolt on its left side is facing the garage door. Loosen the tension nut with a socket wrench but do not remove it entirely.
Lay the replacement chain onto the pulley bar then run it down the bar and wrap it around the pulley. Make sure you keep tension on the back of the new chain as you wrap it around. An assistant's help will make this process easier but is not required.
Use the socket wrench to tighten the tension bolt until the chain no longer visibly sags along the pulley bar.
Press the garage door opener's button to automatically re-engage the slide and deactivate the emergency release. The garage door will be ready for normal use.