Ford Mercury Villager 1997 Owner's Manual page 122

NOTE: Be sure to close all the doors completely. If the doors
are not completely closed, the alarm indicator light will
remain on steadily. The anti-theft system is armed
only when the anti-theft indicator light remains on
steadily for approximately 30 seconds after the last door
is closed, and then flashes every 2.5 seconds.
Disarming an untriggered anti-theft system
Unlock either door with the door key or by pressing the
UNLOCK button on the remote keyless entry transmitter (if
equipped). This will disarm the system. When you unlock the door
with the key, make sure you fully rotate the key in the lock. If
you do not, the system may not disarm, and will trigger when a
door is opened.
If the system is armed and you remain in your vehicle, simply
insert the key into the ignition and turn it to ACC. This disarms the
system and allows you to open the door to exit without
triggering the system. Remember to rearm the system by using
the power door lock or the remote transmitter (if equipped) to lock
the doors.
The remote keyless entry system is designed to work with the
factory installed anti-theft system. It may not work with other
anti-theft systems.
Triggering the anti-theft system
The armed system will be triggered if:
any door is opened without using the door key or the remote
keyless entry transmitter (if equipped)
the liftgate is opened or unlocked
the hood is opened
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