Emergency Local Locksmith · Swanley

Door Mechanism and Gearbox Repair Swanley

Handle lifting but the door will not lock, or has the multipoint mechanism seized? We carry common gearbox and multipoint parts for first-visit repairs where compatible. Locksmith arrival within 30 minutes.

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This service includes

Handle lifts but nothing throws
Handle is stiff or needs forcing to lift
Key will not turn to deadlock, but the handle works
A single hook or bolt not engaging

ETA 30 min

We call if delayed

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Overview

Door Mechanism and Gearbox Repair

This page is for the mechanism behind the handle: the multipoint lock that drives the hooks, bolts and rollers into the frame when you lift the handle, and the gearbox at the heart of it. When that fails you get the tell-tale symptom of a handle that lifts freely while nothing locks. It is one of the most common failures on uPVC and composite doors, and it is a repair, not a reason to replace the door.

If you are not sure the problem is the mechanism, the uPVC door repair page explains how to read the symptoms, and the door lock repair page covers the cylinder and handle. If the mechanism cannot be sourced, we can discuss a full lock replacement, but that is rarely necessary.

What a mechanism repair typically costs

Based on 1,008 real lock and mechanism repair jobs completed by Kingdom Locksmith, with each town row drawn from that town's own jobs. Where only the gearbox case is swapped and the rest of the strip is sound, the price sits lower; a full multipoint strip in a brand-specific pattern sits higher. Ipswich runs dearer, honestly because more of the work there is heavier multipoint and composite failures. We quote before we start.

How a multipoint mechanism works, and how it fails

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When you lift the handle on a uPVC or composite door, you are turning a spindle that drives a gearbox in the centre of the door edge. The gearbox pushes a strip up and down, and along that strip are the locking points: hooks that grab into keeps, deadbolts, and rollers or mushroom cams that pull the door tight. Turning the key then throws the central deadbolt to lock it all in place.

Failures fall into a few clear patterns:

Handle lifts but nothing throws. Gearbox failure. The internal gears or cam have worn or sheared, so lifting the handle no longer moves the strip. This is the classic gearbox fault and it means replacement. Telling it apart from an alignment problem is covered in lock turns but will not lock the door.
Handle is stiff or needs forcing to lift. Alignment strain. The door has dropped, so the hooks fight the keeps. This is the fault that goes on to kill the gearbox, and it is fixed by realigning the door.
Key will not turn to deadlock, but the handle works. That is the cylinder, not the gearbox. See door lock repair, or, if the key spins with no resistance at all, a euro cylinder that spins and will not lock.
A single hook or bolt not engaging. Sometimes a locking point or its keep has failed rather than the whole gearbox, which can be a smaller repair. Where it is the deadbolt that will not move at all, the usual causes are set out here.

How we do it

We diagnose first, because guessing wastes a trip and your money. The locksmith confirms whether the fault is the gearbox, the alignment, or the cylinder by operating the handle and key separately and checking the door in the frame. To fit the right replacement we read the faceplate markings and measure the backset, the PZ dimension (spindle to cylinder centre), and the spacing of the locking points, so the new mechanism matches exactly. Where possible we save the sound parts of the strip and swap only the gearbox case. Crucially, if a dropped door caused the failure, we correct the alignment too, so the new mechanism does not wear out the same way.

French, patio and composite doors

The multipoint principle is the same across door types, but the layout differs. French doors have a mechanism on the active leaf and shootbolts top and bottom on the passive leaf, and either can jam or fail. Sliding patio doors use hook bolts that engage along the frame, and the common sliding-door lock faults are worth reading before you force one. Composite doors run the same style of multipoint as uPVC. We repair and replace mechanisms across all of these, matching the specific pattern rather than forcing in a near-enough part.

Background reading: how a door lock mechanism works, mechanism repair and maintenance, how a French door locking mechanism works, and what it means when the key turns but the door will not unlock.

Where we cover

We repair door mechanisms across Coventry, Derby, Colchester, Ipswich, Burton upon Trent, Nottingham and Leamington Spa, and the towns around each hub. Full prices for every service are on the pricing page.

Call now

Phone 0333 006 9691. Tell us whether the handle lifts but nothing locks, or whether you have to force the handle up, and we will bring the right mechanism. You can also book online.

Door Mechanism and Gearbox Repair, common questions

How much does a gearbox replacement cost?

Mechanism work is priced as a lock repair: typically £192 inc VAT, with most jobs between £120 and £295 across 1,008 real repairs. What moves the price is how much of the mechanism needs replacing. If the strip with the hooks and rollers is sound and only the gearbox case is swapped, it sits lower; a full multipoint strip in an obsolete or brand-specific pattern sits higher. We identify the exact part before quoting, and every figure is on our pricing page.

The handle lifts but the door will not lock. Is that the gearbox?

Almost certainly. The gearbox is the central part of a multipoint lock that translates lifting the handle into the hooks and bolts being driven into the frame. When its internal gears or cam wear out or shear, lifting the handle no longer moves anything, so it lifts freely but nothing throws. The fix is to replace the gearbox with the correct one for your door, which we identify from the mechanism itself.

Can a gearbox be repaired, or does it have to be replaced?

In practice a failed multipoint gearbox is replaced, not rebuilt. The gears and cams inside are precision parts, and once they have worn or sheared, a rebuild would be less reliable and rarely cheaper than a new unit. What we can often save is the rest of the mechanism: the strip with the hooks and rollers frequently stays, and only the gearbox case is swapped, which keeps the cost down.

How do you find the right replacement mechanism?

Multipoint mechanisms come in many makes, backsets, and hook-and-bolt layouts, so fitting the wrong one leaves the door insecure. We read the identifying marks on the faceplate and measure the backset, the PZ (the gap from the spindle to the cylinder), and the spacing of the locking points. That tells us the exact replacement. Where a gearbox is obsolete, there are engineered universal replacements designed to match the common patterns.

Do you repair French, patio and composite door mechanisms too?

Yes. French doors use a multipoint mechanism on the active leaf plus shootbolts top and bottom on the passive leaf, and either can fail. Sliding patio doors use hook bolts driven along the frame. Composite doors run the same style of multipoint as uPVC. We repair and replace mechanisms across all of them, not just standard uPVC front doors.

The door lifts and locks fine but the key will not turn. Different problem?

Yes, that separates the cylinder from the mechanism. If the handle lifts the hooks correctly but the key will not turn to deadlock, the fault is usually in the euro cylinder rather than the gearbox. That is a door lock repair or a cylinder swap. Knowing which symptom you have, handle versus key, tells us where the fault sits before we arrive.

Why did my mechanism fail in the first place?

Most multipoint gearboxes fail because the door dropped out of alignment and was forced to lock every day for months. That constant strain wears the gears until they shear. So while we replace the gearbox, we also correct the alignment that caused it, otherwise the new mechanism wears out the same way. Fixing the cause, not just the symptom, is the difference between a lasting repair and a repeat visit.