screen door lock

the lock on my screen door has suddenly stopped working. Its the kind where, if you're inside, you can flick a lever across to lock it without the key. It can be key locked from inside and outside.

The lever seems to be jammed and the key can't be turned to lock the door. A bit of investigation with the door open indicates that if I press the top of the two metal tongues which poke out of the thin edge of the door ( and when the door is locked engage in the frame ) it seems to free the lever and I can operate the key. However the action of closing the door ( which causes the two metal tongues to retract and spring out again) causes the mechanism to jam again. :confused:

Being a security conscious brit I normally lock the screen door every time I leave the house - so although the lock is only a year old it does get used a lot. What should I be looking for when I dismantle it? Is it likely that some part has worn in such a short time? Any clues anyone?

The top tongue (the little one) isn't supposed to spring out again when the door is closed because there's no hole in the plate on the door frame for it to spring into. At least thats how mine and most others I've seen work. Seems that the small tongue tells the lock if the door is closed or not.

Have you tried lubricating it??

Our screen door behaves like this a couple of times per year, probably due to being exposed to the weather. The first time I disassembled it, now I just give it a squirt of WD-40, another squirt on the key, put the key in and wiggle.

Cheers,
Andrew

Graphite powder is the preferred lubricant for locks and keys. Even thin oils like WD40 tend to make some of the more delicate mechanisms stick.

Mick

thanks guys, i'll try a suitable lubricant. I guess we have had about 5 days of solid rain here last week so that might be the cause.

If you've just had 5 days of rain, it's possibly due to your house moving, especially if you have a clay soil. The clay sucks up the water and the whole house moves up and as the clay dries out the house moves down.

In doing so, it puts the door frame slightly out of skew and as mentioned before the smaller tongue is not being pushed into the door lock enough to release the door locking mechanism. Other than that check to see if your door has dropped for some other reason. Since your door lock failed rapidly, then the above is a more likely cause as being gummed up inside usually causes a slow and extended type of failure to occur.

You can either adjust the door, or move the latching plate, or wait for the foundations to sink again.

My dead latch lock is only just to work properly again as we haven't had much rain in western Sydney for some time up until the last few weeks. My only alternative was to make the bolt hole larger but I didn't get a roundtuit.

From day to day experience the lock is probably OK although a lubrication would help. We only use Silicone spray like most of the locksmiths these days, my recomendation is to lubricate the lock every 6 months. Do not use an oil base such as WD40 or RP7 as they atract dust and cause increased wear.

Your problem is most probably from movement as discussed.
The little top tongue is the relealse for the locking tongue. If the release tongue is not depressed enough when the door closes you will not be able to lock the door.
The main locking tongue needs to be aligned with the hole in the strike plate and not hit any of the timber as it enters the door jamb. We have been adjusting a lot of doors lately because of rain after a long dry. You can move the strike, pack the strike or if easier or for asthetic reasons, you can move the door.

door had dropped relative to the frame ( or frame had risen relative to the door ) so not only was the little tongue not being depressed properly but the big tongue was no longer aligned with the hole by a mm or so.

... the temporary ( as in I'll probably still be doing it next year ) solution is to pull upwards on the door handle as I shut the door - at least I can lock it now. Hopefully all will restore to normality as the ground dries out again. Thanks for all the info on how these locks work.