Multipoint locks are the standard on modern uPVC and composite doors. They provide excellent security through multiple locking points engaging simultaneously. But when they fail, the complexity that makes them secure also makes diagnosis challenging.
How Multipoint Locks Work
Understanding the mechanism helps diagnose problems. For a complete overview, see how multipoint locks work.
The Components
| Component | Function |
|---|---|
| Cylinder | Key operation, turns the cam |
| Gearbox | Central mechanism that converts handle movement |
| Hooks | Curved locking points that grip keeps |
| Bolts | Straight locking points extending into frame |
| Rollers/Cams | Compression devices pulling door tight |
| Connecting bars | Link gearbox to remote hooks/bolts |
| Keeps | Frame-mounted receivers for hooks/bolts |
The Operation Sequence
- Handle lifts → moves the gearbox spindle
- Gearbox rotates → pushes connecting bars up/down
- Connecting bars → move hooks and bolts into engagement
- Key turns → cylinder cam locks gearbox in position
When any component fails, the entire system can malfunction.
"A multipoint lock is only as strong as its weakest component. One failed hook can prevent the whole system from operating.
Common Problem 1: Key Won’t Turn
The Symptom
You insert the key but it won’t rotate, or requires excessive force.
Possible Causes
Cylinder-related:
- Worn cylinder pins
- Debris in keyway
- Frozen mechanism (winter)
- Wrong or worn key
Gearbox-related:
- Gearbox not in locked position (handle needs lifting first)
- Internal gearbox binding
Alignment-related:
- Door pressure preventing cylinder rotation
- Hooks under tension from misalignment
Diagnosis
- Try with door open—if it works, alignment is the issue
- Try spare key—if it works, key is worn
- Lift handle first, then try—gearbox may need setting
Solutions
| Cause | Solution | Cost Estimate |
|---|---|---|
| Worn key | Cut new key | £10-25 |
| Worn cylinder | Replace cylinder | £60-120 |
| Alignment | Adjust hinges/keeps | £50-100 |
| Gearbox binding | Lubricate or replace | £100-300 |
Common Problem 2: Key Turns But Nothing Happens
The Symptom
The key rotates freely but doesn’t operate the lock. The door remains unlocked.
Possible Causes
- Broken cam: The tail piece connecting cylinder to gearbox has snapped
- Cylinder too short: Cam doesn’t reach gearbox
- Gearbox failure: Internal mechanism broken
- Stripped gearbox teeth: Handle doesn’t engage properly
Diagnosis
Does the key turn with noticeable resistance, or spin freely?
- Freely: Cam likely broken or not engaging
- Resistance but no result: Gearbox internal failure
Solutions
| Cause | Solution | Cost Estimate |
|---|---|---|
| Broken cam | Replace cylinder | £60-120 |
| Short cylinder | Replace with correct size | £60-120 |
| Stripped gearbox | Replace gearbox | £150-300 |
Common Problem 3: Handle Won’t Lift
The Symptom
The handle is stuck, floppy, or doesn’t return to horizontal position.
Possible Causes
- Broken handle spring: Internal spring has failed
- Stripped spindle: Square bar no longer grips
- Gearbox failure: Internal spring or mechanism broken
- Door alignment: Bolts under pressure prevent movement
Diagnosis
- Remove handles and test spindle directly
- Check if gearbox spindle turns when handle removed
- Try with door open to eliminate alignment
Solutions
| Cause | Solution | Cost Estimate |
|---|---|---|
| Handle spring | Replace handle set | £30-60 |
| Stripped spindle | Replace spindle | £10-20 |
| Gearbox spring | Replace gearbox | £150-300 |
| Alignment | Adjust door/keeps | £50-100 |
Common Problem 4: Door Won’t Lock Properly
The Symptom
Handle lifts but hooks/bolts don’t fully engage, or some engage but not others.
Possible Causes
- Individual hook failure: One component broken
- Connecting bar detached: Linkage to remote points failed
- Keep misalignment: Hooks can’t reach receivers
- Door drop: Progressive hinge wear
Diagnosis
Visual inspection with door open:
- Lift handle slowly
- Watch each locking point
- Identify which don’t move or don’t reach keeps
Solutions
| Cause | Solution | Cost Estimate |
|---|---|---|
| Single hook failure | Replace mechanism strip | £80-150 |
| Connecting bar | Reattach or replace | £50-100 |
| Keep position | Reposition keeps | £40-80 |
| Door drop | Adjust or replace hinges | £60-150 |
"A door that needs lifting to lock is telling you that alignment is progressively failing. Fix it before it becomes a complete failure.
Common Problem 5: Door Won’t Latch
The Symptom
The door closes but doesn’t click shut. The latch doesn’t engage the keep.
Possible Causes
- Latch not extending: Mechanism issue
- Keep mispositioned: Latch can’t reach
- Door dropped: Latch passes above or below keep
- Latch worn: Bevelled edge no longer catches
Diagnosis
Watch the latch as the door closes. Is it:
- Not moving at all?
- Moving but missing the keep?
- Catching but not holding?
Solutions
| Cause | Solution | Cost Estimate |
|---|---|---|
| Latch failure | Gearbox replacement | £150-300 |
| Keep position | Adjust keep | £30-50 |
| Door drop | Hinge adjustment | £40-80 |
| Worn latch | Gearbox replacement | £150-300 |
The Gearbox Question
Gearbox failure is the most significant multipoint lock problem.
Signs of Gearbox Failure
- Handle feels different (loose, grinding, no spring return)
- Multiple locking points stopped working simultaneously
- Key turns but doesn’t lock/unlock
- Clicking or grinding sounds from centre of door
Gearbox Replacement
What it involves:
- Remove door handles
- Remove cylinder
- Unbolt keep strips
- Slide out old mechanism
- Install new mechanism (must match type)
- Reassemble and adjust
Cost factors:
- Part cost (£60-150 depending on type)
- Labour (1-2 hours typically)
- Type matching (many variants exist)
When to Repair vs Replace
Repair Makes Sense When:
- Single component failure (one hook, cylinder)
- Mechanism is otherwise sound
- Replacement parts are available
- Lock is relatively modern
Full Replacement When:
- Gearbox plus multiple component failure
- Mechanism is obsolete (parts unavailable)
- Lock is over 15 years old
- Security upgrade is desired anyway
The Upgrade Opportunity
If your mechanism needs significant work, consider:
- Upgrading to higher security rating
- Fitting TS007 3-star cylinder
- Installing smart lock compatible mechanism
Maintenance to Prevent Problems
Annual Maintenance
- Lubricate all moving parts with silicone spray—see lock maintenance tips
- Check hinge tightness before they cause misalignment—see uPVC door maintenance
- Upgrade cylinder every 10 years
- Test all locking points for smooth operation
Warning Signs to Watch
- Increasing stiffness anywhere in the system
- Handle taking more effort to lift
- Any locking point hesitating
- Unusual sounds during operation
- Door needing force to close properly
Early intervention prevents expensive failures.
Frequently Asked Questions
What is a multipoint lock?
A multipoint lock has multiple locking points (typically 3-5) that engage when you lift the handle. A central gearbox controls hooks, bolts, and rollers at different heights for superior security compared to single-point locks.
Why do multipoint locks fail more than simple locks?
More moving parts mean more potential failure points. The gearbox, multiple hooks, rollers, and the linkages between them all experience wear. However, their security benefits outweigh this complexity.
How much does it cost to repair a multipoint lock?
Cylinder replacement costs £60-120. Gearbox replacement typically costs £150-300 including labour. Full mechanism replacement can reach £250-400. Individual component repairs may be cheaper.
Can I repair a multipoint lock myself?
Cylinder replacement is DIY-friendly. Gearbox and mechanism work requires specialist knowledge and tools. Incorrect fitting can cause additional damage or security vulnerabilities.
How long do multipoint locks last?
Quality mechanisms last 15-20+ years with proper use. Budget mechanisms may fail in 5-10 years. Cylinder replacement every 10 years is recommended regardless of mechanism condition.
Why does my door need lifting to lock?
This indicates the door has dropped or the locking points are misaligned with the keeps. Hinge adjustment may help, or the keeps may need repositioning. It's a warning sign of progressive failure.
Can I replace just the gearbox or do I need the whole mechanism?
Often just the gearbox can be replaced if the rest of the mechanism is sound. A locksmith can assess whether the connecting bars and hooks are still functional.
Why won't my door latch when I close it?
The latch isn't reaching the keep. This can be door drop, frame movement, or latch mechanism failure. Check alignment first—often the cheapest fix.
Take Action
If your uPVC or composite door is showing any of these symptoms:
- Identify which component category is affected
- Test with door open to isolate alignment issues
- Document exactly what works and what doesn’t
- Act promptly before minor issues cascade
Multipoint locks are excellent security devices—when they work. Understanding their operation helps you maintain that security and address problems efficiently when they arise.