It is always frustrating when the zipper stops working on your favourite pair of boots. You can't wear the boots without the zipper, but it seems like such a waste to toss the boots because of a faulty zipper. In addition, shoe repair shops may charge more than the boots are worth for repair. Fortunately, you can learn to fix or even replace broken zippers to make your boots as good as new.
Figure out why the zipper is not working, as this will decide the steps you need to take toward making repairs. If the pull tab is missing (the pull tab is the piece you grip to pull the zipper up and down) you can easily replace it. Check out fabric stores to find a replacement pull tab that matches the boot zipper. Use a pair of pliers to pry open the crown, which is the piece that holds the pull tab. Insert the new pull tab and pinch the crown closed until the pull tab is secure.
Examine the slider body of the zipper (where the zipper teeth slide through) if the zipper seems to be slipping or catching on the teeth, or if the teeth don't close when you try to zip your boot. If the slider body seems to be pried open so that the gaps between the metal sides are not parallel, this may be the cause of your problem. Use a pair of pliers to squeeze the metal sides back into position so that the sides are parallel, with approximately a 1/8 cm gap between them.
Look at the zipper teeth for problems. Zipper teeth that become dirty or clogged with debris will often cause the zipper to stick or stop working altogether. Use an old toothbrush to clean dirt out of zipper teeth by scrubbing the teeth in both the open and closed position. Examine the zipper for caught fabric or thread if there doesn't seem to be any dirt. Use pliers to pull threads or pieces of fabric out of the zipper teeth, and use scissors to cut away pieces getting in the way of the zipper.
Check for broken teeth in the zipper if none of the previous repairs have worked. There's no way to fix broken teeth, so you will need to replace the zipper. Find a zipper that matches your boot at your local fabric store, and make sure it isn't too short. Longer zippers can always be shortened. Measure the length of the zipper in your boot and remove the zipper by cutting the seam threads and pulling the zipper out. If your new zipper is too long, create a stop at the correct length by stitching the end across the zipper teeth repeatedly. Cut the excess zipper off with scissors beneath the stitching.
Sew the new zipper into your boot. Since boots are usually made of leather or equally heavy material, you will need heavier needles and heavy-duty polyester thread. Install a leather needle before sewing if you are using a sewing machine, or purchase a heavy hand-sewing needle. Using a sewing machine, hold the fabric zipper edge in place along the original seam and run a new seam down each side of the zipper. To sew by hand the seam placement will be the same, but you may want to use a thimble to assist in pushing the needle through the leather to prevent slips and needle punctures.
If you are having trouble finding an exact match at the fabric store for your boot, check out online fabric and craft stores for better selection.