When a window keeps sliding down, the sash balance is worn, mis-set, or disconnected—re-tension or replace the balances to hold position.
Nothing sours a breeze like a sash that slips. The good news: most drop-downs trace back to simple parts inside the jamb—balances, shoes, cords, and pivot hardware. With a little care you can diagnose the fault, decide if it’s a DIY repair, and make the sash stay put again. This guide lays out fast checks, safe steps, and repair options for both newer vinyl/alu units and older rope-and-pulley wood frames.
Why A Raised Sash Falls Down
Single- and double-hung windows use counterbalance hardware to offset sash weight. When that hardware loses tension, disconnects, or breaks, gravity wins and the sash drops. Most modern units use either block-and-tackle or constant-force (coil spring) balances hidden in the side channels. Older wood frames use sash cords tied to weights. Any of these can fail through wear, failed clips, cracked shoes, or frayed cords.
Fast Safety Notes Before You Start
- Support the sash while testing—use a helper or a stick to avoid finger pinch or glass stress.
- Keep kids away from open windows. See the U.S. CPSC guidance on Preventing Window Falls for guards and stops.
- Work on a stable surface; don’t lean out. Gloves and eye protection help when springs are under tension.
Quick Diagnosis Table (Symptoms, Likely Causes, Checks)
Use this snapshot to narrow the fault. You’ll confirm with the step-by-step checks right after.
| Symptom | Likely Cause | Fast Check |
|---|---|---|
| Sash drops the moment you release it | Broken or slack balance spring; disconnected shoe/pivot | Look in side channel: is the shoe engaged? Try lifting; listen for loose spring noise |
| One side drops or sash tilts | One balance failed or slipped off pivot bar | Compare both channels; misaligned or cracked shoe on one side is common |
| Sash moves but feels gritty or jerky | Dirty tracks; dry or seized shoe; worn pulley cord | Shine a light into tracks; check for debris, paint build-up, or frayed cord |
| Sash won’t tilt back in | Twisted spiral; shoe not “reset” to lock position | Rotate spiral/coil tool to set shoe cam; try tilt-in again |
| Old wood unit: rope snapped | Frayed sash cord; weight stuck in pocket | Open side pocket; confirm weight is present and free |
Close Variant: Window Not Staying Open — Common Balance Types
Knowing the hardware style speeds the repair. Here’s a quick rundown of what you might see when you remove the sash or view the side channel.
Block-And-Tackle Balances
This style uses a spring with a small pulley set and cord. When tension fades or clips crack, the sash won’t hold. Replacement is straightforward: match the channel length, stamp code, and shoe style. Trade sources outline the differences between block-and-tackle and constant-force designs and why many modern hung windows use them for smooth lift and hold.
Constant-Force (Coil) Balances
Coil packs store energy in a rolled spring. They mount near the lower third of the jamb and tie into a shoe that grabs the sash pivot. Many units are modular, and some product data sheets note load ranges by sash weight. Pick the right coil pack or stack coils to match the sash.
Spiral Balances
A metal spiral runs inside a tube with a color-coded tip. You set tension by twisting the spiral with a tool, then hooking it to the shoe. If tension is weak, a few turns may restore hold. On old units the tube or spiral can bend or wear out; replacement is simple once length and color code are known.
Rope-And-Pulley With Weights
Classic wood windows route a cotton or synthetic cord over a pulley to a cast iron weight. A snapped rope or jammed weight causes drop-downs. Re-roping with like-for-like cord and freeing the weight brings back smooth, even lift.
Step-By-Step: Test, Identify, Fix
1) Clean And Inspect The Tracks
Open the lower sash a few inches and tilt it in if your window supports tilt. Vacuum the side channels. Wipe with a damp cloth. Avoid waxy sprays; they collect grit. A small dab of dry PTFE on the shoe face is fine if the maker allows it.
2) Check The Shoes And Pivot Bars
Look for a small block inside each channel—the shoe. It has a cam that grips the sash pivot bar. If the shoe sits low while the sash is high, it’s likely disconnected. If the shoe plastic is cracked, replace it. On many vinyl units, you can remove a stop, lower the shoe, and swap it without full tear-down.
3) Re-Engage A Disconnected Shoe
- Support the sash. Release it from the pivot bars if needed.
- Use a flathead or balance tool to rotate the shoe cam to the “unlocked” position.
- Slide the shoe to the correct height.
- Rotate the cam back to “lock,” set the sash pivot into the shoe, and close the tilt.
4) Re-Tension A Spiral Balance
- With sash removed, hook a spiral tool into the tip.
- Turn clockwise to add two to four turns.
- Reconnect to the shoe, then test lift-and-hold at several heights.
If the spiral won’t hold tension or the tube is bent, match length and color code and replace the pair.
5) Replace A Block-And-Tackle Or Coil Pack
- Measure visible metal channel length or read the stamp code stamped on the channel.
- Note shoe style and mounting clip.
- Order matched left/right parts; replace both sides to keep lift even.
- Install per kit steps: attach head clip, set shoe height, connect pivot, and test.
6) Re-Rope A Weight-And-Pulley Window
- Remove side stop and access panel (the “pocket”).
- Pull out the old cord, tie in new sash cord, and fish it over the pulley.
- Tie to the weight; confirm the weight moves freely in its pocket.
- Set cord length so the sash sits tight when closed and balanced mid-travel.
How To Match Replacement Parts
Take clear photos of the balance, shoe, and any codes. Measure channel length end-to-end, shoe width, and sash height. Weigh the sash on a bathroom scale if the balance kit lists weight ranges; place the sash gently on the scale while supporting it.
Stamp Codes And Load Ranges
Stamped numbers like “28C” or “32-3” indicate channel length and spring strength. Match the code exactly or use the supplier’s chart to cross-reference your sash weight. Coil balances list load numbers on each spring; you can stack two coils per side to hit the target.
When To Replace The Whole Balance Pair
Mixed-age parts make a sash drift or tilt. If one side failed, the other isn’t far behind. Swap both sides so lift and hold match. Pairing also avoids repeat trim removal.
Safety And Standards Worth Knowing
Industry standards cover how balances are designed and tested for cycle life. The Fenestration & Glazing Industry Alliance maintains the AAMA 902 spec for sash balances, updated in 2024 to align with the North American Fenestration Standard. If you’re sourcing parts, this gives you confidence the balance style is built for repeated open/close cycles. See trade coverage of the AAMA 902-24 update for context.
DIY Or Pro: Make The Call
Many fixes are within reach if you’re handy and comfortable removing trim. Choose a pro when the sash is oversized, glass is cracked, frame is out of square, or parts are obscure. A repair shop can match odd shoes and pivot bars from a sample and bench-tension coils for you.
What A Technician Checks
- Sash weight vs. balance rating
- Channel straightness and fastener bite
- Pocket access on old wood frames
- Air/water seals after reassembly
Cost, Time, And Difficulty
Parts are modest in price; labor depends on access and trim. Here’s a ballpark guide so you can plan. Replace both sides together for even lift.
| Fix | Typical Parts Cost | DIY Time |
|---|---|---|
| Re-tension spiral (no new parts) | $0–$10 (tool) | 20–40 minutes |
| Replace spiral balances (pair) | $25–$60 | 45–90 minutes |
| Replace block-and-tackle (pair) | $30–$80 | 60–90 minutes |
| Replace coil packs + shoes | $35–$90 | 60–120 minutes |
| Re-rope weight window (pair) | $10–$25 | 60–120 minutes |
| Pro service call | $120–$300+ | 1–2 hours on site |
Troubleshooting Stubborn Cases
Sash Still Slips After New Balances
Two likely culprits: the load rating is too low for the sash weight, or the shoes aren’t locking on the pivot bars. Step up one load size per side or install a second coil where the design allows it. Inspect pivot bars for bends; replace if the tip is chewed up.
One Side Binds Mid-Travel
Look for a shoe rotated into the locked position without the sash engaged. Use a screwdriver to turn the cam back to the open position, slide it to the right height, then re-engage the pivot bar.
Old Paint Seals The Stops
Score paint lines with a sharp blade before prying. Place a thin putty knife under your pry bar to protect the jamb. Reinstall with tiny brads so a future repair is easier.
Weight Pocket Won’t Open
Some pockets are nailed and caulked at the edges. Pry gently and label parts as you go. If the weight is missing, replace with a matched pair or convert to spring balances with a retrofit kit.
Maintenance That Keeps Sashes Holding
- Vacuum tracks during seasonal cleaning; grit chews shoes and guides.
- Keep weep holes clear so trapped water doesn’t rust hardware.
- Wipe coil packs and shoes during any glass cleaning day; dry film lube only if the maker approves it.
- For weight windows, check cords yearly; replace at the first sign of fray.
Parts Checklist Before You Order
- Photos of the entire balance, shoe, and any stamps
- Channel length and depth
- Shoe width, cam style, and color, if noted
- Sash height and exact weight (bathroom scale test)
- Left/right orientation and quantity (always replace in pairs)
When Safety Extras Make Sense
After restoring hold, add stops or guards in rooms with small children. The CPSC link above lists practical options that limit opening width while allowing venting. Window restrictors and guards can pair with balances without affecting normal operation if sized and installed per the maker’s instructions.
Proof You’re On The Right Track
After the repair, raise the sash to one-third, half, and two-thirds of travel. It should stay level at each height, move smoothly with one hand, and sit tight against the sill when closed. Lock should engage without forcing. Any drift points to mis-matched load or a shoe not gripping the pivot fully—easy to fix with a quick re-set or different load rating.
Wrap-Up: A Short Plan You Can Follow
- Support the sash and keep kids away from the area.
- Clean tracks; inspect shoes, pivots, and channels.
- Identify balance type and read any stamp codes.
- Re-engage or re-tension if parts are sound.
- Replace both balances if one has failed; match load to sash weight.
- Test at several heights; add guards or stops where needed.
If you’re comparing hardware styles or want to see how a coil pack is rated for sash weight, product data sheets from makers lay out load ranges and installation notes in plain terms—here’s one example showing constant-force packs and rated loads: Constant-Force datasheet.