Symptoms
- Sash won't stay up on its own
- Feels very heavy or very light to lift
- Uneven movement, tilting slightly as it slides
- Clunking sound from inside the frame
Likely causes
- CommonWorn-out spring or block-and-tackle balanceThese mechanisms lose tension with age and repeated use.
- CommonBalance shoe popped out of the jamb trackThe plastic shoe connecting the balance to the sash can dislodge.
- PossibleWrong tension balance installed previouslyA mismatched replacement won't properly support the sash weight.
- PossibleBroken cord in an older sash-and-weight systemTraditional counterweight systems use a cord that can fray and snap.
What to do
- Open the window and look along the side jambs for the balance mechanism.
- Check whether the balance shoe has slipped out of its track channel and snap it back in if so.
- Note the balance type (spring tube, block-and-tackle, or constant-force) and its length/size stamped on the unit if visible.
- Remove the sash following the manufacturer's tilt-in or lift-out method, which is usually releasing tabs at the bottom corners.
- Unhook the old balance from the sash and jamb, and install a matching replacement, adjusting tension per the package instructions.
- Reinstall the sash and test it holds steadily at multiple heights.
- If both balances on a window are old, replace them as a pair so the sash sits level.
Tools and parts
- Screwdriver
- Tape measure
Window sash balanceSearch: “window sash balance spring replacement”
When to call a pro
Call a window repair company if you can't identify the balance type or the sash won't come out using the standard release tabs.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.