Unusual back door lock.

The back door lock has always been a bit of a puzzle.
In a UPVC door. One full turn and the door is locked but the handle is still floppy. Another full turn and the handle firms up. Another half turn or so before it seems to finish locking.
I don't think I have ever encountered a lock with so many turns between locked and unlocked. I would normally expect all this to happen within 3/4 to 1 1/4 turns.
The lock is now refusing to unlock from the second turn to the first turn without a lot of juggling, cursing, swearing etc. so I am about to take it out and try and get a replacement. Lubrication via the key this morning made it worse instead of better. If locked on the first turn only it seems fine but if you overshoot then it is a lot of hassle. Not good if you want to get out in a hurry!
There is also a stranger little black box on the door which looks like some kind of burgalar alarm. It has 'Semco' as a name on the little lock (we don't have a key) an on/off sliding switch and something that looks like a stereo jack socket. The oblong box also has a spy hole (as it is mounted high and near the door jamb and there is a step down as well I can't see how you would ever see anything useful).
Google finds a Semco alarm which is battery operated (although not like ours) so I am hoping that it is not connected in any way to the door lock!
Wierd to have this on the back door but not the front, although the back door may be older than the front door. Possibly a legacy of owner -2.
The runes of doom keem coming up with "Specialist lock integrated in door. New door please." I am trying to ignore them and will sacrifice a virgin for an alternative reading (although sourcing one may be a problem around here).
Cheers
Dave R
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On 11/03/2010 09:05, David WE Roberts wrote:

First turn throws the bolt as for a conventional mortice lock.

Second turn (and a bit) throws the mechanism on the multi-point bolts. You should see this happening if you lock the door whilst it's open.

There are loads of different manufacturers of UPVC door locks. Each has his own variation on mechanism.

Something is broken or very worn either inside the main lock case or between the main lock case and the satellite mechanisms.
so I am about to

OK
Sounds like a coincidence.

New door only if you get to the point where you can't open the door at all and you trash the door getting it open!

www.dgsupplyline.co.uk
HTH
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The lock mechanism is Yale. The door is Everest. There isn't the usual surface plate with lugs that you see on most modern doors - there is a concealed bolt which engages top and bottom when you raise the handle. Turn the key one turn and the lock goes out but the handle isn't immobilised. Turn the key a second time and the handle is immobilised. There is then another part turn and the lock goes out a bit further for no apparent reason.
I have replaced the Yale barrel (undo one screw and the whole thing pulls out of the side of the door) with an after market replacement. The barrel just has a short bar which rotates inside the lock meachanism and works arcane magic (or not). The new barrel went in and seemed to work O.K. Closed the door, locked it, and now it won't unlock. So there is something in the main mechanism which is jamming up.
I have no idea if the main lock mechanism can be extracted and repaired/replaced (assuming I can open the door again).
Runes of Doom are looking suspiciously accurate.
http://forums.moneysavingexpert.com/showthread.html?t "3683 from 2006 makes depressing reading - allegedly Everest wanted 150 just for a new handle mechanism.
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<snip>
Use of judicious force (on the principle that if it was screwed anyway then a broken key wasn't going to add much) got it open again.
Another strip down and oil and WD40 into everything I could access and the lock seemed to work O.K. with the door open, although it could be induced to jam sometimes by applying lateral pressure to the tounge(?)/bolt of the lock when fully extended.
Put it all back together and the door wouldn't lock.
Checked the alignment and the lock was right at the bottom of the striker plate - presumably a minor re-alignment when lubricating was now preventing the bolt shooting. Lost of jiggling and juggling couldn't get it to lock.
So I filed out the striker plate to make more room for the bolt and now it seems to lock and unlock O.K. (so far)
Looking at the alignment (or not) of various components and screw holes (including the fact that there was a spacing washer at the bottom of the plate covering the lock mechanism but not at the top to get it to align with the door) I concluded that the installation had always been marginal and probably pressure on the bolt had gradually worn the internals until they started to jam.
I am now hoping that the mechanism will last until we redo the back of the house in a year or so at which point the back door will be filled in.
Another day gone without major progress on the shed but I didn't fancy having a back door that I couldn't unlock.
Cheers
Dave R
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On 11/03/2010 15:34, David WE Roberts wrote:

Actually, it sounds as though the front edge of the door has dropped (which is why you needed to file the strike plate) and put the top/bottom locking out of alignment as well.
It sounds as though you have done all the right things. You should be aware that the top and bottom strike plates are also adjustable and further, you can screw the top and bottom bars/rods in and out to adjust their effective length.
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