Why won't my UPVC door handle lift?

The most common reason is a failed gearbox inside the door. The gearbox is what the handle operates to engage the locking points. When it fails, the handle either drops, will not lift, or lifts but does not engage the locking bolts. A gearbox replacement fixes this.

My UPVC door won't lock from outside but works inside — what's wrong?

This usually means the cylinder is failing, not the gearbox. The cylinder drives the locking mechanism from outside when you turn the key. If the key turns but nothing engages, the cylinder driver blade may have worn. A cylinder replacement is the typical fix.

Can I fix a UPVC door mechanism myself?

Simple lubrication is a DIY job. Gearbox and handle replacements require removing the door furniture and door panel — feasible for a confident DIYer with the right parts, but getting the wrong gearbox brand or size is common. Misalignment and seized mechanisms are better left to a locksmith to avoid door damage.

How long does a UPVC gearbox last?

Most UPVC gearboxes last 10–20 years with normal use. Doors fitted in the 1990s and 2000s are now reaching the end of their gearbox life. Coastal properties and doors exposed to weather tend to fail sooner due to corrosion.

Photo by Max Vakhtbovych / Pexels

upvcadvice

Why Won't My UPVC Door Lock? The 6 Most Common Causes

A UPVC door that will not lock is almost always one of six things: a failed gearbox, a misaligned door, a worn cylinder, a seized mechanism, a dropped handle, or a faulty keep. Here is how to tell which one.

James Mitchell

5 June 2026 · 7 min read

## Start here: is the door itself the problem?

Before assuming the lock mechanism has failed, push the door firmly against the frame while lifting the handle. UPVC doors can drop on their hinges over time, meaning the locking points no longer align with the keeps in the frame. If the door locks when pushed but not when released, it is a door alignment issue, not a lock failure.

If the door locks fine from inside but not from outside, or the handle has stopped working altogether, read on.

Cause 1: Failed gearbox

The gearbox is the most common failure point. It sits inside the door and translates the handle movement into the engagement of the locking bolts. When it fails, you typically get one of:

- Handle drops under its own weight - Handle will not lift (stiff or solid) - Handle lifts but the bolts do not engage (floppy at the top of the travel)

A failed gearbox is a replacement job, not a repair. The gearbox brand needs to match the door — ERA, Winkhaus, Yale, Fuhr, Fullex, and Mila are common on UK UPVC doors. Fitting the wrong one means the bolt positions will not line up with the keeps.

Cause 2: Worn or failed cylinder

If the handle works fine but turning the key does nothing, the cylinder is the suspect. The cylinder has a driver blade that engages the mechanism. This blade wears down over time, particularly on doors that are locked and unlocked frequently.

Cylinders are also the point of attack if the door has been targeted. A cylinder that has been forced, even unsuccessfully, may turn but not engage.

Replacement is straightforward — it is a 20-minute job — but get the right size. Measure centre-to-centre from the screw hole in the middle to each keyhole. That gives you the cylinder dimensions.

Cause 3: Door misalignment

UPVC door hinges adjust in three directions. Over time, doors drop — usually at the latch side — and the locking bolts no longer line up with the keeps in the frame. The keeps are the metal plates the bolts shoot into.

You can often diagnose this by looking at the gap around the door. If the top latch-side corner has a wider gap than the hinge side, the door has dropped.

Hinge adjustment is the fix, not a new mechanism. The bolts are fine; they are just aiming at the wrong spot.

Cause 4: Seized or corroded mechanism

UPVC mechanisms need lubrication. A mechanism that has never been lubricated, or that sits in a damp environment, corrodes internally. The first sign is that the handle becomes progressively stiffer over months. Eventually it stops moving.

Try a PTFE-based lubricant spray along the door edge where the bolts emerge. Work the handle repeatedly. If it frees up, lubrication was the issue. If it remains stiff, the gearbox may need replacement.

Do not use WD-40 on UPVC mechanisms. It strips existing lubrication and attracts dust.

Cause 5: Broken or damaged keeps

The keeps are the metal cups in the door frame that the bolts shoot into. If a keep is loose, damaged, or incorrectly positioned, the bolt will not seat properly and the door will not lock under load.

Check this by watching where each bolt goes when you lift the handle slowly. If a bolt is slightly high or low relative to the keep opening, the keep needs adjusting or the door needs realigning.

Cause 6: Handle mechanism failure

Handles themselves can fail independently of the gearbox. The spindle — the square bar that runs from the handle through the door to the handle on the other side — can snap, strip, or pull free from the gearbox coupling. This produces a handle that turns freely but does nothing.

A stripped or broken spindle is usually visible when you remove the handle — look for a square bar with worn or rounded corners.

When to call a locksmith

Lubrication: try it yourself. Handle and gearbox: call a locksmith unless you are confident with the measurements and sourcing. Anything involving the door frame, keeps, or hinge adjustment: call a locksmith. Getting the alignment wrong can damage the frame.