Things You'll Need
Metal zippers can only withstand so much use before the teeth stick together or otherwise break. The zippers on your couch cushions rub up against the fabric constantly, every time you shift or move. Any spills or accidents on the couch that reach the zipper cause rust, which stops the pull from sliding along the teeth. Simple fixes might solve the broken zipper problem, but the process may require a little more work if the zipper breaks off the cushion.
Grab the zipper pull and gently work it down to the bottom of the zipper. Place the pliers flat against the zipper pull and press down. Move the pliers to the other side of the pull and press again. Try sliding the zipper pull closed.
Look over the zipper and identify any uneven teeth. Even a single off-center tooth stops the pull from closing the zipper. Squeeze the tooth with the pliers until it sits flush with the surrounding teeth and try pulling the zipper pull.
If other methods do not work, lay the seam ripper flat against the fabric on one side of the zipper. Slide the ripper along the fabric, tearing off one side. Use the seam ripper on the opposite side, removing the zipper from the couch cushion. Leave a piece of fabric from the original zipper approximately 1/2 inch to 1 inch long on the bottom of the cushion where the original zipper sat.
Pull the cover off the cushion. Leave the cushion facing right side out and set the new zipper on the cushion, making the bottom of the zipper sit directly on top of the fabric piece. Insert sewing pins along the sides of the zipper, attaching the fabric on the sides of the zipper to the cushion.
Hold the cushion flat as you slowly push it through the sewing machine, stitching the zipper to the cushion. Use a zigzag stitch or another strong stitch that keeps the pieces firmly attached. Add a second row of stitching for extra protection and repeat the process on the opposite side of the zipper.
If the zipper pull fell off, replace it with a small charm. Use thin-gauge wire, like that used in jewelry making. Wrap the wire around the charm and push the wire through the hole in the zipper top. Twist the wire around and trim off any extra wire with wire cutters.