You need to use stringent safety measures for garage door torsion spring repair. If you do not use the right tool you can loose fingers, limbs, or even your life.
Replace and Install the Torsion Spring
The broken torsion spring can be replaced with a new one with these basic steps.
For safety always assume that the spring is going to break and the cone is going to slip or explode as you wind and unwind the spring.
Unplug the power chord of the opener and disengage it from the door.
Gather supplies and working instruments.
Measure old and new springs. Never touch the winding cones and don't grab the spring.
Mark torsion shaft. To level the garage door after the new springs are installed these marks will help.
Unwind old spring that is not broken. Never touch a set screw without properly inserting a fitting bar into the winding cone.
Loosen and remove the bolts that secure the torsion cones to the spring bracket.
Replace the torsion springs.
Install the torsion hardware back again.
Wind new garage door springs.
Check and lube garage door.
To avoid unnecessary risk you can always use the help of a professional. This installation process can be dangerous, so it's best to err on the side of caution.