It's inside the door next to the door latch. look for the wires and connector running to it.
This door switch is a very very common cause of interior lights staying on/ coming on intermittently while driving door the road - false door ajar warnings - and random alarm going off, and the door locks acting like they're possessed by jumping beans.
That's the bad news... The good news is liberal amounts of spray oil / lubricants is the fix.
See "Related Questions" below for more about getting those sensors under control.
Anyone looking for the 'door jamb' switch is having problems with the false door ajar warnings.
This is extensively covered in the "Related Question" below...
The drivers side kick panel is in the drivers footwell , just ahead of the drivers door It is an interior trim panel by the drivers left foot
near the fusebox (drivers side interior)
It's the interior trim panel , just in front of the drivers door
chilton manuals at parts store
under the instrument panel on the drivers side ( and the Power Distribution Box is in the engine compartment on the drivers side )
On a 1996 Mercury Mystique : There are ( 2 ) kick panels They are the interior trim panels , in front of the front doors , beside the drivers and front passengers feet
In the trunk on the drivers side in the corner fender skirt under the interior carpet.
On a 2000 Mercury Mystique : The fuel pump shut off switch ( inertia switch ) is in the drivers footwell behind the kick panel ( The interior trim panel in front of the door by the drivers left foot , there is an access hole through the panel )
ITS UNDER THE DASHBOARD ON THE DRIVERS SIDE. YES YOU HAVE TO STAND ON YOUR HEAD TO SEE IT.
Open the drivers door and in the drivers end of the dash you will see a small removable plastic fuse panel cover , the fuses are behind the cover
I'm assuming it would be in the same location as on a 1999 Ford Explorer - under the vehicle , below the drivers door , mounted in the frame rail
On a 1997 Mercury Mountaineer ( V6 and V8 ) Bank 2 is the drivers side of the engine