If the spring is broken, there is not tension on it. The reason for the spring is to lift the weight of the door, all but a few pounds so the will close.
I can not stress this enough, if you dont know what your doing, DONT TOUCH IT!!!!
Yes I know capitols is yelling, I was.
I have a frind that is missing 3 fingers and part of his hand from messing with one of the springs. Not to mention he was pinned to the spring for about an hour until he was missed by his wife.
Just call a professional to come and repair it. The couple hundred you spend on it is better than the hospitol bill.
It's a torsion spring, I see the broken spring. I just wanted to be able to lift the door to get the truck out. After a google search looks like these things are dangerous to mess with.
.....I am not messing with it, will call the experts in the morning.
Had mine go a few months back, for the extra bucks get both springs replaced, will save you the service call when the other one goes, and it will.
I think most respectable professionals would refuse to replace just one.