Repair a garage door can be confusing and so in some instances expert help may be required. However, there are a few simple things you can check before calling a service professional.
Recruit some back-up. Spring system repair is much more complicated (and dangerous). You will need a helper, and should support the door while servicing springs. Make sure you have safety cables threaded through the center of coil springs for safety. These old-style springs weaken with time and can break without warning, so use extreme caution!
Don’t get in over your head. If you are in doubt as to how to repair a garage door, by all means call a pro. Garage doors are heavy and the springs are highly tensioned, and you do not want to risk an injury to yourself or others.