You probably open and close your window blinds every morning and evening, so any problem with their operation becomes a daily source of annoyance. Try these steps. Keep in mind that most do-it-yourself repairs on blinds void the warranty.
Lower the blind and adjust the slats to the open position using the tilt cord or wand.
Unclip and remove the blind from its brackets. Lay it flat on a large table or other work surface. Follow the steps below as far as your repair requires.
Remove any end caps and the cover on the bottom rail to expose the knots or clips that secure the ends of the lift cord and ladder tape or string ladders.
If you are replacing the ladders, disconnect them. Otherwise just disconnect the two lift-cord ends, which are clipped or tied to the rail.
Pull both lift cords up through the slats as far as needed to remove any damaged slats and feed new ones onto the ladders. Thread the cords back down and secure them to the bottom rail. Then install the cover and end caps.
If you are replacing the ladders or lift cords, pull the cords up to the head box.
To replace the ladders, disconnect them from the tilt tube in the head box and slide them off the sides of the slats. Slide the slats into the new ladders and attach the ladders to the tilt tube and bottom rail. Thread the lift cords through the slats, alternating back and forth between the ladder rungs, and secure them to the bottom rail.
To replace a lift-cord, pull both ends up into the head box, over the pulleys, down and out. If you don't have another assembled blind to refer to, sketch a simple diagram before taking them out.
Feed the two ends of a new lift cord back into the head box and over the first pulley. Direct one end over the next pulley and the other one across the head box to the far pulley. Feed both cords down through the slats to the bottom rail and secure them. Install any cover or end caps.
Hang the blind.
If you've installed new cords, level the bottom rail. Depending on the model, either adjust the lift-cord equalizing buckle or knot the two cords together just above the tassel when the bottom bar is level. Cut the cords, if necessary.
If you are replacing venetian-blind cords, you may also cut the replacement into two pieces at least as long as the originals (one is longer than the other), and tie or tape them to the ends of the old cords so you pull the new ones through as you pull the old ones out. A lift cord on a venetian blind may be two separate cords or one that is looped at the grasped end. While the cords are out, give the slats a good cleaning. It will never be easier!