What are common uPVC door lock problems?

The Master Locksmiths Association's guide lists the usual reasons a uPVC door will not lock even with the door open: gearbox failure, which it lists as the most common, a damaged multipoint lock, an alignment problem, a problem with the cylinder, and a door that needs lubricating. If the door only refuses to lock when it is shut, the same guide puts that down to alignment.

The gearbox sits in the middle of the door behind the handle and drives every locking point. When it starts to fail, the handle tends to flop, crunch, jam halfway or refuse to go down at all. The MLA guide says a handle that will not push down at all is most commonly a failed gearbox, and that a gearbox is cheaper to replace than to repair.

Along the edge of the door, a hook, roller or mushroom can break, and the MLA guide says the complete multipoint lock is then replaced. The cylinder is a separate part. A published locksmith guide says that if the key turns freely and nothing happens, the cylinder cam may be broken or the cylinder too short. If the key meets resistance and nothing happens, the gearbox is not responding.

Alignment problems are the ones that come and go. uPVC expands in heat and contracts in cold, and the MLA guide says being 1mm or 2mm out is enough to stop a door locking or unlocking. It also warns that poor alignment adds wear to the gearbox and multipoint lock, so a door left out of line can end up with a mechanism fault as well.

A floppy handle that will not spring back usually points to a worn spring, spindle or gearbox rather than the handle itself, and the MLA guide says it is quite rare for the handle to be the fault. Tightening loose handle screws is safe to try, but one locksmith guide notes that it will not fix every loose handle.

Related questions

• Why does my uPVC door lock when I open it but not when I close it?
• Can you replace the locking mechanism on a uPVC door?
• Why won't my uPVC door handle lift up?