A customer in Isleworth got in touch because the aluminium bi-fold patio door had developed an intermittent locking problem.
This particular multipoint system was key-operated, which makes correct door alignment especially important because excessive resistance is transferred directly through the key and gearbox components.
On inspection, the door was out of alignment and the customer had been having to force the key to turn.
That extra strain had eventually damaged one of the toothed wheels inside the gearbox.
It was a specialist gearbox that I did not carry in van stock, so I ordered the correct replacement for the following day.
Once the new gearbox was fitted, I adjusted the keeps in the frame so the locking points lined up properly and the key could operate without being forced.
The bi-fold door was then locking and unlocking smoothly again.
With this type of system, a key that becomes noticeably harder to turn is worth dealing with early. Correcting the alignment before the gearbox fails is much cheaper than waiting for internal components to break.
