Replace Constant Force Window Balances

Before ordering anything, measure the jamb channel the sash rides in, the pocket where the old balance sits. QUICKTILT balances need at least 1-1/4" (32 mm) of width and 9/16" (14 mm) of depth. If your channel measures up, the window can be converted even if its original hardware went out of production years ago. While you're in there, note whether a vinyl cap covers the balance pocket. It matters in step 6.

Channel a touch under 9/16" deep? The balances can still work, with a trade-off. On the back of each balance is a plastic piece that pushes outward against the channel when the sash tilts, which is what holds a tilted sash still. In a channel that's slightly too shallow, that piece binds and the sash jams every time you try to tilt it. We've worked on a window system like that, and removing the plastic piece from each balance fixed it. The window worked normally in every other way.

What you give up: the sash can no longer lock itself still in the tilted position, which makes cleaning the glass a lot harder. Setting the sash back in (step 10) gets trickier too, because the balances move around instead of staying where you set them. It takes some patience, but you can get it in. If your channel is well short of 9/16", send us photos through Identify My Part before you buy.

Press in both tilt latches at the top of the sash and tilt it down to 90°. Raise one side upward to free that pivot bar, then work the other side out. The video pulls both sashes; the repair itself only touches the broken one.

A well-designed balance system lets the pins lift straight out. The system in the video encloses its pins in a closed hole, and the window locks in the open position, so freeing the first corner took real force.

If yours fights the same way, it's the hardware design, not your technique. Keep a grip on the glass and work one corner at a time until the pin clears.

Only the window being repaired needs this step. Before any screws come out, take the spring load off each old coil balance: slide a flathead screwdriver into the pivot shoe and turn it 90°.

Hold the screwdriver firmly. Releasing the lock instantly frees the coil, and depending on the sash weight the shoe can shoot up the track hard. Safety glasses on for this one.

Some balances state their strength on the housing: a stamped 4 means a 4 lb spring. If yours shows a legible number, match it and skip the scale. The old balances in the video carried no markings, so the sash got weighed: stand it on a bathroom scale and read the total.

Each of the two balances carries half the sash weight, so divide the reading by two. A 30 lb sash takes a pair of 15 lb balances. When the split lands between strengths, go up: a 15 lb sash halves to 7-1/2, and while a 7 lb pair might carry it, it can fall short of holding the sash open. Buy the 8 lb pair instead. The video's 17 lb sash runs on two 8 lb balances, and step 10 is where you confirm your pick holds.

Our QUICKTILT balances come in 1 lb steps from 4 lb to 24 lb. The "Add parts to cart" button asks for your sash weight and suggests the right strength. They sell as a matched left-and-right pair, so one order covers one sash.

The old balance system in the video used its own proprietary pins, so the sash needs standard pivot bars before the new shoes will grab it, one per bottom corner. Most hung sashes carry their pivot bars exposed on the bottom face; this window hid them under a cover.

Unscrew the old bars, line the ends of the new bars up where the old ones sat, mark the fresh screw holes with a pencil, and drive the screws straight in.

No pilot holes needed. Window vinyl is soft enough that screws seat cleanly without cracking it.

Most hung windows have a vinyl cap covering an opening where the balance slides out. This window had the cap but no opening underneath, so the retrofit means making one.

Where the cutout goes matters. Put it at the end of the track the sash reaches when the window is fully open, not where it sits when closed. A sash that closes at the bottom gets its cutout up top. The sash being repaired in the video is the upper one, which closes at the top, so its cutout sits at the bottom of the channel.

Mark the top of the cap with a pencil and pop the cap off. Hold the new balance against the channel to size the cutout, then shrink the opening by 3/4" or a touch more. That leaves the cap enough material to snap back onto. Score four horizontal cuts to define the top and bottom of the cutout, then make the long vertical cuts between them. The horizontal cuts act as stops and keep the blade from running past the line.

This is sharp-knife work inside a slippery vinyl channel. The cut-resistant gloves on the tool list are for exactly this step.

No vinyl cap on your window? Place the cutout by the same rule, then cover it. Don't leave the hole open: as the sash slides past it, the sash can tilt slightly to one side, and a tilt latch can catch and snap off when you close the window. The best fix is a 3D-printed cap that snaps over the hole. No 3D printer? We can print a custom cap for you. Measure the width of the channel, decide how tall you want the cap, and send us both numbers for a quote.

With the tension already released in step 3, back out the old balance's screws and slide it down toward the cutout and out of the channel. The pair in the video sat tight, and a set of pliers helped pull them free.

While the channel is empty, vacuum the track clean before the new hardware goes in.

Turn each new pivot shoe so its opening faces you. That disengages the lock and lets the balance slide freely. If your balances are marked with an L or an R (the one in the video reads 8L), the L goes on the left side and the R on the right.

Slide the balance up the channel and fasten it through the original upper screw hole. The old balances used two screws each; the video reuses only the upper hole, which keeps the new balance high enough that the window still closes fully without interference. Snug the screw and stop. Don't overtighten.

Insert the flathead into the new shoe and pull it about halfway down the track. That leaves working room for the sash. Turn the screwdriver so the shoe opening faces upward, which re-engages the lock. Repeat on the other side and match the heights exactly: the sash needs both pins to land at once.

Rest the sash's pivot bars into the two shoe openings with the sash at 90°, then tilt it up toward the frame until both tilt latches snap into the channel. Run the window up and down a few times. This is where the strength you picked in step 4 proves out. If the sash drifts down or won't hold position, swap in the next strength up.

If the sash jams when you tilt it, check the channel depth. A channel just under 9/16" does exactly that, and step 1 covers the fix.

Snap the vinyl caps (or your printed caps) back on and give the channels a shot of silicone spray. If other windows in the house still run older coil balances, spray those coils too while the can is out. It does a lot for how they slide.

Then the other sash (the one that kept its old balances) goes back in, and it's the fiddly part. Set its balance shoes so the left pivot bar seats into its shoe first, lower the right side until that pin just touches the bottom edge of the right shoe's opening, then lift the left side of the sash. The lift pushes the right pin down into its shoe. Close the window and you're done.

If your balance or shoe doesn't match the ones here, send us a photo through Identify My Part and we'll match the exact replacement.