A reader wants to repair a broken spring in a 1980s double-hung window. (Reader photo)

Q: I live in a 1980 rancher with original wood, non-tilt, double-hung windows. I was raising the lower sash to let in fresh air when I heard a loud noise, like a metal spring breaking, and the heavy sash came crashing down. I am lucky I still have fingers! Some of the other windows creak loudly and are difficult to open. The top windows do not seem to move at all. The identification number on the windows is MW 1-80. The windows look very good for their age — no leaking, fogging or wood rot — despite the windows always being in the shade. The wood trim has been stained, not painted. How do I fix this?

Manassas

A: That noise you heard probably was a breaking spring. Antique double-hung windows used rope and steel weights to counterbalance the sashes (the moving, framed window sections) so they could be left open without risk of slamming shut. But this left relatively big air gaps near the pulleys, so modern windows — including ones made in the 1980s — usually depend on spring balances that fit tightly into the jambs (the side tracks).

Replacing most types of spring balances is easy, requiring only a screwdriver or sometimes just a twisting motion with your hand. But some types of balances don’t come out easily; you actually need to destroy the old mechanisms to remove the sashes and install the new hardware. And there is the whole issue of finding replacement parts because spring balances come in dozens of different types. Some are still available; others are not. Even when replacements are available, the manufacturer might be different so the part numbers don’t match.

There are two ways to proceed. The simplest option is to call a company that repairs windows and leave the rest up to them. Full Service Glass in Manassas (703-530-9124; fullserviceglass.net ) will send a technician to your home to examine the window and determine whether it can be fixed. If it is possible, the company would then try to find replacement balances and give you a cost estimate. The company charges a minimum of $150 to $180 per visit but waives the fee for the initial visit if it can’t find a replacement part or if you go ahead with the repair work. You would need to pay it, however, if the company tracks down a replacement part but you don’t hire them to do the work. Replacement balances vary in cost from about $25 to $125.

 Or you can try to do the repair yourself. In this case, begin by calling the manufacturer, if possible, to see what replacement parts you need. Some windows have no identification marks, while others are clearly marked with the name of the manufacturer, or they have letters and numbers in a corner. Window-supply companies or an Internet search can help you decode these.

 The MW on your windows is code for MW Manufacturers in Rocky Mount, Va. MW was sold to Ply Gem Industries ( plygem.com ) in 2004 but is still in business as a division of that company.

Carlana Barnes, field service coordinator for Ply Gem Windows, said MW used two types of balance mechanisms on wooden, double-hung windows with non-tilting sashes in the 1980s. If you’re lucky, you have the type where you can extract the lower sash by pushing it up and then sideways far enough into the jamb on one side to free the other side. (First remove the jamb covers and pull up the takeout clips.) Then you should be able to see and extract the balance mechanisms. Watch YouTube tutorials on replacing window spring balances to get an idea of some of the ways these come out.

If you can’t extract the sashes by pushing them sideways, Barnes said, you have a trickier window style. You would need to pry off the narrow wooden stops at the sides and top, and fold the balance mechanisms in half, breaking them.

MW switched window styles around 1993 and no longer carries either type of balance. Barnes recommends contacting Blaine Window Repair Service in Silver Spring. (301-565-4949; blainewindowrepair.com ) or Strybuc Industries in Philadelphia (800-352-0800; strybuc.com ). Both companies carry a wide array of window parts, including dozens of spring balances, and help customers identify the parts they need.

If replacement balances aren’t available, you have a couple of options: Leave the window as-is and just don’t open it; order a sash replacement kit, which comes with new jamb liners and balance mechanisms, as well as a new sash; or order a new window, the priciest option of all.