OLD-FASHIONED double-hung windows, found mostly in homes built before World War II, depend on heavy counterweights to allow the sashes to be raised and to prevent them from sliding downward when released.
The weights are inside cavities in the sides of the window frame. Cords through pulleys at the tops of the window tracks link the weights to the upper corners of the sashes.
The system is simple. However, when, the cords break or become entangled, repair involves disassembling the window.
To replace or untangle sash cords, you must first remove the lower sash. To do this, carefully pry one of the strips of stop molding away from the jamb; there are two such strips, each forming one side of the window tracks for the lower sash. Use a wide, stiff-bladed putty knife. Then pivot the sash toward the inside of the room and wiggle it loose from the opposite track.
IF you only intend to untangle unbroken cords, be careful not to dislodge their ends from the grooves in the sides of the sash. Have a helper grasp the cords while you remove the ends, using long-nosed pliers to withdraw the small nail at the end of the cord. Tie a large knot in each cord where it emerges from the pulley hole to prevent the cord from falling into the cavity.
To replace cords attached to the upper sash, you must remove it also. If there is access to the outside of the window, you may be able to remove the sash by prying away a strip of stop molding there and proceeding as described for the lower sash. If not, you will have to remove one of the parting strips (the molding attached vertically in the center of each jamb to separate the window tracks).
First, lower the upper sash. Also, slice through any paint covering the seam between the parting strip and the jamb, using a putty knife or chisel. Then grasp the strip near the top with sturdy pliers and pull it at right angles away from the jamb.
To avoid marring the wood, drill a small hole and install a screw about a half-inch deep into the strip and pull on that. This will dislodge the top of the strip from the groove. Then slip the blade of a putty knife behind the strip and gently pry along its length to remove it. Now withdraw the upper sash.
Access to the cavities is through a hole near the bottom of each jamb. The hole is usually covered by a removable wooden access plate; such plates are fitted very skillfully and may be difficult to find, particularly if the tracks have been painted.
Screws may hold plates in place, but usually the plates are designed so that pressing against one end causes the other end to pop out. If you cannot find a plate, install a screw in the inner window track about eight inches above the sill. Then pull on the screw, using pliers. This should loosen a friction-fitted plate if it has been covered by paint. Avoid prying at the seams, for the ends of plates are easily marred.
At times, a strip you do not wish to remove overlaps a plate. Saw through the strip horizontally below the raised upper sash and remove the plate with the strip attached. If no access plate is present, open the cavity by removing the inner casing. Inside each cavity, the weights should hang side by side and travel freely as sashes are operated.
If the cords are entangled, untwist them. If their travel seems restricted, check for obstructions protruding into the cavity. If a cord is broken, it and the weight will have dropped to the bottom of the cavity. Replace broken sash cords with weights.
If the pulleys at the top of the window track are made of metal and their groove is large enough, chain can be used. However, if the pulleys are made of wood or have only a narrow groove, use cord. Use the broken cord as a guide in determining the lengths of the replacements, or cut lengths of chain equal to the length of the window jamb, plus about five inches.
Insert a nail through the last link of a chain segment and feed the other end over the pulley and into the cavity. Draw the end out through the access hole and thread it through the eye in the top of the weight. Secure the chain by tying it with thin wire. Then place the weight back in the cavity.
To attach the chain to the window sash, have a helper steady the sash on the window sill, where the bottom of the sash rests when it is fully lowered. Pull the chain until the weight rises to the top of the cavity, then allow it to descend about an inch. Use one or two small screws to anchor the chain in the groove in the upper edge of the sash, then snip off the extra chain below the screws.
Next, fit the window back into its track and test it. The sash should rest firmly on the sill when lowered. When raised, the weight should stop an inch or two from the bottom of the cavity.