Place scale under the garage door on the side of the door with the broken extension spring.
How to chage springs on garage door.
This video will help you weigh a garage door with extension springs.
Once in place disconnect the garage door opener.
Open the garage door to remove all spring tension and clamp it in place.
Use a piece of tape to mark the current placement of the pulley so that it.
Place the new garage door springs against the garage door position the springs so that the ends are facing you and coming from opposite directions.
The left spring should have the wire coiling from the left the right spring should have the wire coiling from the right.
One cable attaches to the bottom of the door runs up and over the pulley above the door and around the spring pulley and then attaches to the door track bracket.
One at the end of each spring and one at the top of the vertical door track they also have two cables on each side.