'Adjusting Garage Door Torsion Springs' should not be attempted by most homeowners. They can be very dangerous.
The problem is that they have to be worked on when the door is down and the springs are under tension. When you release the set screw you have to have a rod in place and be holding it to control the force of the spring. Adjusting garage door springs of this type is not recommended for the average homeowner.
WARNING!! Torsion Springs can be VERY DANGEROUS, Precautions and thorough knowledge are REQUIRED!!! Do not attempt this repair without the proper skills.
There are those die hard do it yourself pros that insist on doing everything themselves. Are you one of those? Well then you should check further online for instructions. Clopay a manufacturer of residential garage doors has some instructions that may apply to your situation, Supplement to Torsion Springs, follow this link to check it out. There is another article that gives you and in depth discussion of this type of spring. The article provides installation instructions for springs and adjustment information, Torsion Spring Information.
I have been in construction most of my life and I personally know a few garage door installers. I have worked on torsion springs and I must confess that it made me nervous. I will not relate some of the horror stories, however, I will say that people have been seriously hurt, messing around with this type of spring.
Before you call a garage door serviceman, write down exactly what the door is doing. Verify by examining them that the springs are not broken. Springs either work or the don't, there is not much in between. Write down the width and height of your door and the type of springs you have. Ask for a quote over the phone for a cost on adjusting both springs. Make sure you specify both. Sometimes they will try to quote you for one spring and want to charge you double when they show up.
Call at least three places and try to make sure they are actually different places. Get quotes from all three. If they won't quote it over the phone, call someone else. A door that works, but does not close all the way does not need to be replaced. Make up your mind that you are not buying a new door. You be the judge if you want to be sold new springs. For another seventy-five to one-hundred dollars you can have new springs and the adjustment is free.
Torsion springs have cycle ratings. The minimum is 10,000 with the highest being 100,000. Get quotes for new springs at the same time. Remember, ask for both of them. Ask about the cycles and get the longer lasting ones if you can. Buying new springs when they just need to be adjusted is your decision. Weigh the age of the door and the cost when deciding.