Whenever a spring breaks, the door will not go up. Attempting to lift a door with a broken spring can be extremely dangerous. Attempting to replace the springs yourself is even more dangerous. You should never attempt to fix a broken spring yourself – only experienced, trained professionals should ever touch torsion springs.
Replacing a spring requires expertise to know exactly which spring to replace it with. The correct springs are determined based off the weight of the door. There are hundreds of combinations of springs but only one is correct for your door. It is important to have the correct springs to prevent an array of problems in the future. With the wrong springs, your opener will break much quicker and your door is more likely to come off tracks. It is alarming how many installers use the wrong size springs.
Knowing which springs to use can only be determined by experience.