I have a 406 estate on a 52 plate, fantastic car, but just one problem, when I lock the car it often manages to unlock itself, when open the door the alarm goes off, switch the ignition on and the alarm stops. When I lock it with the button on the key fob I can hear all the doors lock, but when I go to unlock in the morning it is already unlocked. Any clues.
by any chance do you chuck your keys down on a shelf, or in a bowl when you come in doors after parking it up, I ask this because I used to chuck mine in a bowl with lots of other keys, and occasionally I would go out in the morning and the car was unlocked. I put it down to the remote button being pressed as it drops in the bowl. I now place them on the sideboard and it has been fine ever since.
The central locking will fail-over to and unlocked state if one door isn't closed properly and failed to engage the deadlock.
Try locking the car with the key fob then pressing the 'lock' button again within three seconds. This will lock the car without deadlocks. This will give you an indication of whether it's a dead lock problem.
After a recent trip to the tip I found some crud in the boot lid lock. Make sure this is clean on your car as it would prevent the boot lid locking properly.
Other than that, five minutes with some WD-40 on all the locks etc would be certainly worth while.
Other than that, it could be an electrical issue but at this stage, I doubt it.
One other thing, maybe the key fob has an issue. Try moving it well out of range of the car at night.
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