Lift the handle with the door open. If it lifts freely, the lock works and the door has moved out of alignment, so adjust the keeps on the frame. If it resists with the door open, the fault is inside the lock. That one test decides everything you do next.
Open the door fully and lift the handle. Nothing else diagnoses a uPVC door faster, and it costs you ten seconds.
With the door open, the lock has nothing to fight. The hooks and bolts throw into thin air, so the handle should lift smoothly with light resistance. What happens next tells you where to work.
Work out which row you are in before you go any further. Half the failed repairs on uPVC doors come from adjusting the hinges when the answer was a keep, or forcing a handle when the gearbox had already gone.
A uPVC door runs a multipoint lock, which means one handle drives several closing points at once along a strip down the closing edge of the door.
On our entrance doors, the handle drives a three point closing mechanism. Turn the handle upward to engage the top and bottom closing points, then lock it with the key. Turning the handle downward releases all three points at once.
Our terrace and French doors work on the same principle with an espagnolette. The handle drives the closing points, and the receivers on the frame set how firmly the door pulls in.
For the differences between lock types and standards, our guide to front door locks covers that ground.
Adjust the frame side, not the lock itself. The lock case is a sealed mechanism, and what you can move is where its hooks land.
One keep at a time. Moving all three because the handle felt stiff leaves you with no reference point and a door that locks worse than when you started.
Bright metal scrapes on a keep tell you where the hook is hitting. Follow the marks rather than guessing, and you will usually finish in two adjustments.
Reduce the compression. A handle that needs a shove is pulling the door harder into the seal than the mechanism was built to manage, and the gearbox pays for it eventually.
Back the keeps outward by a millimetre, away from the door. That gives the hooks a fraction more room and takes the load off the handle.
Then check the door is not simply sitting too low. If the gap along the top of the door widens towards the handle, the door has dropped and the hooks are hitting the keeps from below. Our guide to adjusting a uPVC door covers the hinge side of that job.
Get the door hanging square first, then set the lock. Doing it the other way round means adjusting the same keeps twice.
The closing points never engaged, so the key is locking an empty mechanism. Lift the handle fully to its stop before you turn the key, and listen for the points seating.
If the handle will not reach its stop, the hooks are hitting the keeps. That is an alignment job, not a lock job.
If the key spins a full circle with no resistance at any point, the cylinder cam or the gearbox has failed. Neither is adjustable, and both are replacement parts.
One more possibility worth ruling out. On a euro cylinder, a key that turns but does nothing sometimes means the cam has sheared, and the door will still open from inside while offering no security at all. Treat that as urgent rather than annoying.
Your door has moved with the temperature, and the lock is reporting it. Both PVC and timber expand in heat and contract in cold, which changes how hard the leaf presses into the frame.
Our own product guide treats this as a seasonal adjustment. On our doors, the receiver on the frame may need adjusting between summer and winter, which you do by bending the tongue inward or outward until the door closes firmly against the frame.
Set it for the season you are in. Expect to move it back the other way in six months, and treat that as maintenance rather than a fault.
A cold snap can also thicken old lubricant. If the lock stiffens overnight in a hard frost, try lubricating it before you adjust anything.
Rollers, sometimes called mushroom cams, sit on the closing strip and turn to change how deeply they sit in the keep. Grip the roller with pliers and rotate it a quarter turn, then close the door and test.
Turning the roller so its wider face meets the keep increases compression. Turning it back reduces it. That gives you fine control without moving the keep at all.
Not every uPVC door has adjustable rollers, so check before you reach for pliers. If the closing points are hooks or deadbolts rather than round cams, the adjustment lives in the keeps instead.
The gearbox has failed, and no adjustment brings it back. A handle with no resistance means the cams inside the lock case have sheared, so the handle is no longer driving anything.
Stop using the door as normal and get the lock case replaced. A failed gearbox often leaves the door closed but not actually locked, which is a security problem rather than an inconvenience.
Take three measurements before you order a replacement. The backset from the edge of the door to the centre of the keyhole, the centres between the keyhole and the spindle, and the overall faceplate length. Getting those wrong is the usual reason a replacement lock does not fit.
Once a year at minimum. Our maintenance guidance is to lubricate hinges, handles, espagnolette locks, slide bars, roller bolts, slots and locks with an all-purpose oil.
Apply it to the closing points and the keeps, work the handle several times, then wipe the excess off the faceplate. Oil that sits on the strip collects grit.
Keep it off the weather seal, and keep it off the slide rails of any friction brake. Our guidance is explicit that friction brake rails stay clean, oil-free and free from paint, because oil stops them gripping.
Ten minutes a year prevents most of the stiff handles that turn into replaced gearboxes.
Some faults sit outside what a screwdriver reaches.
Adjusting the hardware is normal maintenance, and our own product guide treats hardware adjustment as a finishing detail rather than a manufacturing defect. If you think a lock has failed on a door we supplied, contact us rather than dismantling it.
