A local customer in Walton-on-Thames called because the door would no longer lock properly.
The key would not turn far enough to complete the locking cycle and could not be withdrawn normally.
Once I removed the key-operated multipoint gearbox, the cause became clear. Small metal fragments inside showed that the mechanism had suffered internal failure.
This type of system operates the multipoint locking points by turning the key itself, so poor door alignment can put a great deal of extra strain through the gearbox.
If the door is not sitting correctly in the frame, that resistance can eventually lead to worn components, broken parts or even damaged keys.
The failed gearbox needed replacing, so I sourced the correct part and returned the following day to fit it.
After replacement and testing, the door was locking and the key was operating normally again.
