If both springs are the same length the garage door should be level across the floor.
How to install double garage door extension springs.
Be sure the door is open and supported when doing this.
Following are the steps necessary to replace one or more of these springs while taking safety precautions.
Release the tension on side mounted extension springs by lifting the door and locking it in place on each side with a pair of locking pliers.
Garage door springs offset the weight of the door and allow it to open and close with ease.
Other problems frequently ensue when a single spring is used on a double car garage door.
If the extension springs are not the same length open the garage door and change the location of one of the s hooks so that when you close the door both springs are the same length.
If the spring breaks near the stationary cone a large portion of the spring spins loose with the winding cone secured to the shaft.
Tie the extension spring to the roller track then detach the cable from the bottom bracket with a pair of pliers.