Symptoms
- Sash slides shut under its own weight
- Needs a prop stick to stay open
- One side seems to droop before the other
- Sudden onset after years of working fine
Likely causes
- CommonFailed spring or tension balanceThe balance loses tension over time and can no longer support the sash weight.
- CommonBroken sash cord (older double-hung windows)The rope that connects to a counterweight has snapped.
- PossibleBalance shoe disconnected from the trackThe connector piece can pop loose without the balance itself failing.
- Less commonSash heavier than the balance ratingAdded glass, storm panels, or paint buildup can overload an aging balance.
What to do
- Confirm which side is failing by lifting the sash slowly and watching for one side to droop first.
- Check for a disconnected balance shoe in the track and reseat it if it's simply popped out.
- For spring balances, look for a visible tension adjustment (a notch or screw) and try increasing tension slightly per manufacturer guidance.
- If tension adjustment doesn't help, plan to replace the balance cartridge, matching size and weight rating.
- For older cord-and-weight windows, remove the interior stop molding to access and replace the broken cord.
- Reassemble and test the sash at multiple heights to confirm it holds without a prop.
- Avoid leaving a window propped long-term, since it's a safety and security risk and stresses the frame unevenly.
Tools and parts
- Screwdriver
- Pry bar
Window sash balance kitSearch: “window sash balance replacement kit”
When to call a pro
Call a window repair pro if several windows are failing at once or the weight pocket for a cord-and-weight system is hard to access.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.