When a window won’t lock, check alignment, the latch parts, and the handle drive before any replacements.
A stuck latch isn’t just annoying. A window that won’t lock can rattle, leak drafts, and invite risk. The good news: most fixes are quick once you match the symptom to the cause. This guide shows simple checks you can do in minutes, then step-by-step repairs for the main window styles.
Window Will Not Lock: Causes And Quick Checks
Start with a fast triage. You’re looking for three things: alignment, part condition, and smooth movement. Work from easiest to hardest.
| Symptom | Likely Cause | What To Try |
|---|---|---|
| Handle moves, latch won’t grab | Keep/strike out of line or worn cam | Clean, lube, then shift the keep a few millimeters; retest |
| Locking tab hits frame edge | Sashes shifted or balance shoe slipped | Raise or lower the sash until tabs meet; reset the balance shoe |
| Handle spins with no bite | Square spindle sheared or gearbox fault | Remove handle; replace spindle or the gearbox |
| Snib turns but feels gritty | Dirt or dried grease inside mechanism | Vacuum debris; apply silicone spray to moving parts |
| Locks only if you push up | Minor misalignment | Support the sash while locking; adjust hinges or keep for a lasting fix |
Tools And Materials You’ll Use
Keep a small kit nearby: Phillips and flat screwdrivers, hex keys, a drill/driver with small bits, silicone spray, dry PTFE lube, cotton swabs, a putty knife, a small file, ruler, pencil, and spare handle spindles. A headlamp helps inside narrow frames.
Safety And Warranty Pointers
Wear gloves and eye protection when drilling or filing. Don’t remove sash limiters on upper floors. If your unit is still under warranty, check the maker’s lock guidance first. Many brands publish repair steps and parts pages; a clear example is the Andersen help note on a handle that moves but won’t lock, which lists keeper checks and part swaps.
Step-By-Step: Double-Hung And Single-Hung
Check Sash Height And Tabs
Slide the lower sash up an inch, then pull it down until the meeting rails kiss. Watch the latch tabs; both should meet the keep cleanly. If one sits high or low, alignment is off. On many vinyl units the balance shoe can pop free, leaving the sash tilted and the lock out of line. Reseat the shoe and retest the lock travel.
Realign The Keep
Open the sash. Mark the current keep position with a pencil. Loosen the screws a quarter turn. Shift the plate by a millimeter or two toward the latch side. Tighten, test, and repeat in small moves. If the latch still grazes the edge, use a small file to ease the keep mouth, then smooth the burr.
Restore Smooth Travel
Blow out dust from the meeting rail. Wipe the latch cam and tabs, then add a small burst of silicone spray. Cycle the lock ten times. Chips and dust can stall the cam. Check screws for correct bite depth.
Step-By-Step: Sliding Windows
Square The Panel
Roll the sash to the center. Sight the gap at the head and sill. If the gap changes end to end, the rollers may be out of level. Lift the sash to unload the rollers, adjust the screws a turn, then test the lock again. A level sash helps the hook land in the keeper every time.
Move The Keeper
If the lock still misses, shift the keeper a hair toward the hook. Use the same mark-loosen-shift-test loop. A tiny move—two millimeters—can bring the hook home.
Step-By-Step: Casement And Awning
Check Hinges And Pull-In Pressure
Open the window a few inches. Watch the gap along the hinge side as you turn the crank. If the sash binds or shows uneven gaps, the hinge arms may need a tweak. Many brands provide adjustable hinges; a small turn can bring the sash back into square so the lock can engage cleanly.
Inspect The Multi-Point Keepers
Most casements use mushroom cams that pull into metal keeps. If the handle turns but keeps don’t capture, look for shiny rub marks around the keeps. Loosen the screws, shift the keep toward the cam path, then retighten. If the handle turns with no pull, check the handle spindle and the gearbox.
Step-By-Step: Tilt-And-Turn
Set The Hardware To Neutral
On tilt-and-turn units the handle drives a full perimeter strip. Set the handle to the six o’clock position. Close the sash. Now try the lock throw again. If the cams still miss their keeps, adjust the mushroom cams a notch toward the frame until they pull in cleanly.
Bring The Sash Back Into Square
Use the hinge adjustment screws to nudge the sash up, down, or side to side. Take small moves. Retest after each change. When the gap lines stay even, the lock will land without a shove from your shoulder.
Step-By-Step: uPVC Espagnolette
Confirm Handle And Spindle
Pop the cover plate, remove the two screws, and pull the handle. Inspect the square spindle. If it’s rounded or snapped, replace it with a matching length. Handles and spindles are low-cost and designed for simple swaps.
Service The Gearbox
With the handle off, look at the gearbox in the strip. If the cam won’t travel, the box may be seized. A short burst of silicone can free dried grease. If travel still sticks, replace the gearbox. Many shops stock direct-fit parts and outline steps to diagnose, lubricate, adjust hinges, and set the keeps. uPVC lock guide.
When The Frame Or House Has Shifted
If a lock only lines up when you push the sash upward by hand, the frame may be slightly out. You can still gain a clean lock by shifting the keep, adjusting hinge screws, or easing a tight spot with a file. If large gaps show and drafts have appeared, note the change and call a pro to check the frame.
Troubleshooting Flowchart
Follow This Order
Move in this sequence to save time and avoid part swaps you don’t need.
- Clean, lube, and test.
- Check alignment: do the latch parts meet?
- Shift the keep a millimeter or two; retest.
- Inspect the handle spindle; replace if worn.
- Open the sash and check hinge level and travel.
- File tiny burrs; smooth rough edges.
- Replace the gearbox or lock strip if still failing.
Signs You’re Done Right
The handle closes with a firm, smooth finish. The latch pulls the sash snug with no extra push from you. No scuff marks appear near the keep. The meeting rails sit flush, and the lock clicks without force. No play shows at the handle.
Care Tips That Prevent Sticking
- Vacuum dirt from tracks every season.
- Use silicone or dry PTFE only; skip oil that collects grit.
- Wipe cams, tabs, and keeps twice a year.
- Keep paint off strike plates and moving parts.
- Log tiny shifts early; small tweaks keep parts from wearing out.
Add a quick seasonal maintenance checkup.
Lubricant And Cleaner Tips
Silicone spray leaves a dry film that resists dust. PTFE sprays work well on cams and gearboxes because they don’t stain. Avoid heavy oils; they draw grit and can gum up the cam path. If old paint covers a keep, score edges with a knife, lift the paint with a putty knife, and polish with a fine file.
When To Call For Service
Stop and book help if the sash scrapes the frame, if glass sealant has split, or if you see movement at the jambs. A trained tech can reset hinge shoes, swap a lock strip, or shim the frame. Makers also publish care and repair pages; a clear guide from Brennan shows checks for casements, hinge arms, and locks, plus when to bring in a tech. Brennan guide.
Security And Child Safety Notes
Locks deter easy entry and keep kids from pushing sashes open. Keep cords on shades secured and fit stops or guards where kids play. The National Safety Council posts window fall tips and blind cord advice you can act on today. NSC window safety.
Parts You Can Replace At Home
Many lock fixes use common parts. Match like for like, measure twice, and keep the old piece as a pattern at the store.
| Part | Typical Signs | DIY Level |
|---|---|---|
| Handle + spindle | Handle spins, no latch movement | Easy |
| Keep/strike plate | Latch misses the pocket | Easy |
| Gearbox/lock strip | Cam won’t travel or jams mid-throw | Medium |
| Rollers (sliders) | Sash tilts; lock hits off-center | Medium |
| Balance shoe (hung) | Sash height mismatched at meeting rail | Medium |
| Hinge set (casement) | Uneven gaps; poor pull-in | Advanced |
Common Snags And Fix Moves
Handle Moves But No Lock
Look at the keep. If cams don’t enter, shift the keep toward the cam path in tiny steps. If nothing moves inside the strip when you turn the handle, the spindle or gearbox is likely at fault.
Lock Works Only On Cool Days
Heat can expand frames, and a tiny shift changes alignment. Move the keep toward the latch by a millimeter or two so it works across seasons. Keep lube thin to limit drag.
Latch Scrapes Paint
Mask the keep, scrape paint from the mouth, and smooth the edge with a file. Paint on the keep can block the cam from reaching full throw.
Proof You’re Following Safe Guidance
Brand support pages outline fixes for a handle that moves but fails to lock, including keeper moves and part swaps, plus links to order parts. Public safety sites lay out window fall tips and blind cord rules. Linking those resources here gives you direct paths to maker steps and safety rules while you work for reference.