Sliding Patio door will latch but key won't lock it Post your questions and get answers concerning many areas of this subject

[Lesolee]

Apologies if I use the wrong names for items.

The sliding door slides shut. The lever engages the multipoint latching mechanism so the door can’t open, but the lever is free to be unlatched. The key will not turn in the lock to prevent the lever from moving.

Diagnostic: If the door is open the lever cannot move to the up (lock) position. However, if the little interlock button (see image) is pressed the lever will bring out the latches, and the key will turn in the lock to prevent the lever from moving (unlatching).

History: The patio door was fitted by professionals but the lock never worked. They would not come back and fix it. A locksmith came out and turned the latching strip (on the non-moving door frame) upside down and it worked for a couple of years. Now it has stopped working.

It is my Aunt's door, so it is a 15 miles drive to try anything! I tried a little block on the fixed door frame to ensure the little button was pressed in case something was out-of-tolerance there. No success. The lever seems to move up as far with the door open (and button pressed) as with the door closed.

I can't figure out why it won't lock after being latched closed.

[stoneyboy]

Hi lesolee,
From your description the problem is adjustment of the latch plates and/or the door itself. Try lowering the running wheels (so the door is raised up) there are normally screws for doing this beneath plugs at low level either side of the door.
Regards S

[Lesolee]

Thanks. I will give that a try next time I visit.

[Lesolee]

I went online to find a video of how to adjust the wheels. Looked easy. The place for the screw adjusters does not seems to exist. It is just a gaping hole.

The back end doesn't look any better.

There are no plugged holes along the bottom either.

The latching strip looks as though it is slid down to the maximum extent.

It is unclear what happens when the screws in non-slotted locations on the latching strip are slackened.

[stoneyboy]

Hi Lesolee,
Unfortunately you will not be able to tell how many times the latching strip has been “adjusted” until you remove it.
If you are feeling brave and there are two of you, you could try lifting the door off it’s tracks so you can see how the runners are adjusted. Do this with the door half open, there may be a block screwed to the top of the door edge which you will have to remove first.
Regards S

[Lesolee]

I am not brave, and there are never two of me.

If I slacken all the screws in the latching strip, then remove the two in slots, will the latching strip slide up/down or are the other screws also screwed directly into the frame?

[Lesolee]

As a follow-on question, the latching strip has three score lines on it (red line), and I can see the impression where the interlock button strikes the latching strip (blue line).

They are offset from each other by at least 1 cm (1/2 inch). Do you suppose they are meant to be aligned? (Having an alignment mark would make sense to me.)

[stoneyboy]

Hi lesolee,
Before you adjust the latch strip operate the locking handle with the door open (push the interlock pin in) nearly close the door - leaving a gap You should then be able to see if the latching strip is in the right place to engage with the latching hooks.
You can then decide whether trade help is needed.
Regards S

[Lesolee]

Thanks for the tip.

[Lesolee]

It is not possible to see the alignment when the door is almost closed. The mechanism is set back into the frame so it is all hidden. Instead I marked the frame with a sharpie to show the alignment. (The camera is giving an excessive parallax error.)

There are four latch points. First the top one, T.

Then the upper of the two middle ones, M.

The alignment seems excellent (my markings are not so good on the moving frame since they are distant from the sliding latches). It is not like the latching strip can be slid 1 cm or more. The tolerance is at the millimetre level.

There is nothing wrong with it as far as I can see :-(