My garage door goes up about 3" and stops. What could be the cause?

More than likely it's a broken spring. If it's a torsion spring (on a bar above the door) we do not advise the customer to touch it. There is a lot of torque on the spring and it could easily cause physical damage (in other words, hurt you!). If there are two springs, they should both be changed as they both get the same amount of use with the opening and closing of the door.