Replacing sash cords in older double-hung windows is an easy task, once the window stops have been removed.
Step 1: The piece of trim along each side of the window frame is called a window stop. Use a carton knife to cut along the edge of the window stop. Use a stiff putty knife to pry the window stop trim pieces from the window frame.
Step 2: Slide the window sash up and prop it open. Remove any metal window track on the lower portion of the window.
Step 3: Locate the counter weight access panels on either side of the window frame. If there is parting stop blocking the panel, remove it using the carton knife and putty knife as before.
Step 4: Once the window stops and parting stops have been removed, remove the window sash from the window frame. Detach any remaining sash cord from either side of the window sash and set the sash aside.
Step 5: Remove the counter weight access panels and locate the counter weights within the window frame. Access panels are typically held in place with a screw near the bottom half of the panel.
Step 6: Untie the old sash cord from the counter weight and remove the old cord.
Step 7: Cut a piece of cotton sash cord roughly the same length as the old sash cord. Tie a string to one end of the new cord and tie a screw or weight to the other end of the string. Drop the weighted string over the window pulley located near the top of the frame. Fish the string out of the access panel and pull the sash cord over the pulley and down into the access panel.
Step 8: Remove the weighted string and tie the new cord to the counter weight.
Step 9: Set the window sash atop the window sill. Attach the new cord to the window sash. Tie a knot at the end of the sash cord so the counter weight dangles 3 inches above the window sill when the sash is fully opened.
Step 10: Once both sash cords have been replaced, allow the weights to hold the sash in its open position. Install the access panel doors, parting stops and metal window tracks.
Re-attach the window stops using oval head screws and finishing washers to allow easier access for any future repairs.