You need not panic with zipper problems. The part of the zipper which receives the most abuse is the slider. Hundreds of slides cause the slider to wear, thus causing faulty locking of the zipper teeth. Most often zippers can be rejuvenated by simply replacing the slider. These are some things that you should also consider:
If teeth are not fish scaling or missing, it’s probable that a slider is all that’s required.
If the zipper separates after zipping, just a slider may be in order.
When buying zippers, match the quality of zipper to its use. We carry metal or plastic zippers in many different sizes.