Your curtain's pulley systems will stop working eventually as the cord's get tangled, wear thin or break. The easiest way to fix this is by replacing the curtain cord with fresh cord. The curtain will start working like new again and will last for years. Restring the cord yourself to save money, and be sure to replace any broken parts from the curtain's assembly if you find any.
Measure the length of the curtain rod while it is mounted on the wall with a measuring tape. Then measure the distance from the floor to the rod. Take note of the measurements. Add the two numbers together. Add an extra 6 inches to the results. Double the final number. This how long your replacement cord needs to be.
Remove the curtain rod from the wall by unscrewing the brackets on either end of the rod. Slide the curtains off the rod. Keep the screws handy.
Pull any old cord out of the curtain rod. Cut the curtain cord free if it is tangled.
Lay the curtain rod on a flat surface with the end hardware facing up.
Feed the end of your new cord under the top pulley at the left end of the rod. Work the string into the rod's track and out of the opening in the track. Hook the cord with an open paper clip to help pull it out.
Push the cord under all the sliders into the track.
Feed the cord under the master carrier that slides on the rod and then work it out through the first hole on the top of the carrier. Use the paper clip to work it through. Tie a double knot in the end of the cord once it's out.
Work the unknotted end of the cord between the two pulleys on the same end that you initially started on. Slide this end under all of the sliders.
Slide the cord under the master carrier so it goes all the way through. Slide it under the second carrier and bring the end up through the first hole in the carrier. Feed it back down through the right hole in the carrier.
Work the cord under the remaining sliders, keeping the cord in the track as you work.
Feed the cord between the two pulleys at the right end. Pull it down and through. Feed it back up through the far right side of rod's insider end.
Loop the cord back around and feed it through the small hole at the top of the bracket so it slides back into the rod's track.
Work the cord under all the sliders as you bring it back toward the left of the rod. Bypass the carrier on the right side by sliding it straight underneath.
Feed the cord under the first part of the carrier on the left, then bring the cord up through the second hole from the right. Use the paper clip to assist you. Tie a double knot in the end. Pull the strings tight so there isn't any slack in the rod.
Mount the rod back on the wall and hook the curtains onto the sliders.