Fixing a broken window counterbalance on a double-hung window
Photo 1: Remove the sash
Remove the window sash from the vinyl track. The sash has to be low and level before you lift the first side out of the jamb liner.
Close-up of Photo 1
The little metal cam on the bottom corner of your sash will brake the locking terminal that’s under tension inside the track
Photo 2: Release the pawl
Start by employing a safety step: Release the tension on the undamaged sash balance. Insert a screwdriver on the locking terminal and twist clockwise to release the pawl. Brace yourself—there will be immediate upward tension.
Photo 3: Raise the locking terminal
Slowly raise the locking terminal and let it rest at the bottom of the balance cartridge.
Photo 4: Remove the jamb liner
Remove this type of vinyl jamb liner by working a stiff putty knife between the window stop and the track. Grab the vinyl edge with one hand, then pry the knife outward to release the jamb liner and avoid damaging the wood stop.
Photo 5: Slide out the bad cartridge
Study the jamb liner components and how they’re put together. Determine which is the top end of the jamb liner and which is the sill end (the angled cut). Remove the foam cap at the top, release the S-clip and slide out the crippled balance cartridge. Remember which balance cartridge came from which channel of the vinyl jamb liner. The cartridge with the shorter S-clip is always installed on the exterior side of the window.
Photo 6: Replace a broken locking terminal
CAUTION! Parts under tension. Wear safety glasses for this step. To install a new locking terminal (the place where the nylon cord is properly strung in the pulley system), start by firmly clamping the balance cartridge to a workbench. Pull out 6 to 8 in. of cord, position a locking pliers at the bottom of the cartridge, clamp the cord end—to resist spring tension—then thread the cord through a new locking terminal. Tie a knot on the end of the cord, grab the terminal, release the pliers and slowly retract the locking terminal to the bottom of the cartridge.
Photo 7: Reassemble the balance
Position the locking terminal at the end of the cartridge so the pawl is facing up and toward what is the room side of the window opening. Slide the cartridge down the center of the channel in the vinyl jamb liner and hook the S-clip over the top of the track. Replace the foam cap and reinstall the vinyl unit into the window opening.
Imagine this: You’re taking one of your wood double-hung window sashes out of its frame when suddenly and violently, the spring-loaded balance releases and snaps up into the vinyl jamb liner. The first time this happens, you stand there in shock. Then you notice broken plastic parts on the floor and that there’s no longer any tensioning force to hold the sash open after you put the sash back into the window jamb liner (or track). You must decide if you’d prefer to let a pro handle this repair. If so, search online or look in the Yellow Pages under “Windows, Repairs.” Search for outfits specializing in a range of window repair work, and avoid the listed hardware stores that may only replace broken glass. If you fix this yourself, choose one of the following three repair options (depending on the damage you identify and/or your skill level):
- Replace the whole vinyl jamb liner unit (Photos 1 – 4)—including both balance cartridges. This is the simplest but most costly approach. If you’re a beginning do-it- yourselfer, go this route.
- Replace only the balance cartridge that was broken (Photos 1 – 5 and 7). This inexpensive repair is for intermediate skill workers.
- Take apart the crippled balance cartridge, replace the broken locking terminal and (sometimes) restring the pulley mechanism (Photos 1 – 7 and Fig. A). Tackle this only if you’re a highly experienced do-it-yourselfer.
First, get the repair parts. (Note: The parts and the repair techniques are different for wood windows and all-vinyl windows.) Double-hung wood window hardware may vary by brand. To make sure you get the right parts, first refer to any product literature you may have. Then order repair parts from the manufacturer through the dealer where you bought your window. If the original part sources are unknown, you can buy generic parts over the Internet. If you’re going to buy either the entire vinyl track unit or just the damaged balance cartridge, copy the number stamped on the cartridge’s face (inset, Fig. B). This number is the glass size code for your window; a parts retailer can’t fill your order without it.
Whichever repair option you choose, if it’s a wood double-hung window, you must first remove the vinyl jamb liner unit from the window frame.
- Our window was a factory-made unit, not an older window retrofitted with vinyl tracks.
- Each type of window has a different method for jamb liner installation.
- Our jamb liner came out of the left hand side of the window opening. For right-hand side jamb liners, reverse any instructions calling for turning a screwdriver clockwise or counterclockwise.
Carry out the steps relevant to your repair in Photos 1 – 7.
When the repair is complete, reinstall the vinyl track in the window frame. Reset the tension on the sash balance by reversing the earlier steps. Release the locking terminal’s pawl, lower the terminal down to a point about 10 in. from the windowsill and twist your screwdriver counterclockwise to lock the terminal in the vinyl jamb. Carefully install your window sash by positioning one cam, then the other, onto the top of each locking terminal. Next, level the tipped sash, then raise the sash top and snap it back into the vinyl jamb liners.
Finally, lower the installed sash, and the braking pawls on each side of the sash will be released. Now that the window sash is under spring tension, return it to a fully closed position.
Figure A: Anatomy of a Window Balance
Our window uses a “block-and-tackle” balance. Each window has four balances, two per jamb liner. If the locking terminal is broken, the cord in one block-and tackle mechanism may have snarled. To restring the pulley system, use a pliers to grab the top of the tensioning spring and detach it from the holding pin. Once the pulleys are restrung, run some cord out the bottom of the balance, clamp it with a locking pliers and reconnect the pulley block to the spring. Insert the holding pin and install a new locking terminal (Photo 6).
Figure B: Glass Size Code
Record the glass size code stamped on the balance cartridge. If you replace the whole cartridge, you’ll need this code to order parts. Note the position of both the locking terminal and the braking pawl before the unit is installed in the jamb liner (Photo 7).
Required Tools for this Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
- 4-in-1 screwdriver
- Putty knife