It is a common occurence for frustrated backyard mechanics to post a question to the effect of "My domelights stay on constantly on my late model ford vehicle. Where is my door ajar switch located? I can't find it. Help!!!"  on ford related discussion groups. A question to the effect of "My door handle doesn't open the door anymore. How do I fix it?" also is asked from time to time. This article contains information that would be useful to someone troubleshooting the above mentioned problems or someone just interested in how their vehicle works.

Below are some pictures of the front drivers side door latch for a 1998 ford crown victoria police interceptor and the door ajar switch. The latch (F8AZ-5421813-AA) pictured below will fit multiple other vehicles:

92-97 Mercury Grand Marquis
98-01 Ford Crown Victoria and Mercury Grand Marquis
98-02 Lincoln Town Car
86-97 Ford Aerostar
86-91 Ford Taurus & Merury Sable
88-94 Lincoln Continental
88-94 Ford Tempo & Mercury Topaz
92-95 Mercury Sable

Note that not all vehicles listed above will have the door ajar switch located on the latch, some such as the aerostar will have the conventional door jamb pin switch.

The latch pictured above is currently in the unlatched, door ajar position. When the latch is installed in the door, the majority of the latch is concealed behind the door sheetmetal and the interior door panel and not visible to the vehicle operator.

like the previous picture, the latch pictured above is in the unlatched, door ajar position but the picture was taken from a different angle

above latch is in the door closed and fully latched position

above picture like the previous is in the door closed and fully latched position, but the picture is taken from a different angle

here is the back of the door latch. when installed in an actual vehicle, this part of the latch is entirely concealed behind the door sheetmetal and the interior door panel and is invisible to the vehicle operator.

Take note of the yellow insulators, this is where the connecting rods for door handles and lock buttons connect. The one in the lower left is for the interior door handle, the one above it is for the lock button. On the lower right, there is a lock lever as well, both the exterior door lock cylinder and power lock solenoid connect on this side. The big yellow/white connector above the lock lever is for the exterior door handle. Unlike the interior door handle connector, the exterior door handle connector will not open the door unless the lock lever is in the unlocked position.

the black/tan device in the upper left hand is the door ajar switch.

same latch as above, but with the door ajar switch removed. the grounding terminal is present because the door hinges are not a reliable ground path to the vehicle's chassis.

In the 1995 model year, crown vics started using a door ajar switch located on the latch itself instead of the conventional door jamb location. When the latch is fully closed, a raised portion of the top portion of the latch slider arm pushes the button on the switch up which electrically closes the switch and sends a ground signal the vehicle's computer meaning that the door is closed.

above are a couple pictures of the actual door ajar switch. the part shown lists for less than $10 at the dealer and is easy to remove once the door panel is off, just remove one screw and twist the switch then unplug the electrical connector. installation is the reverse of removal.

above are a couple pictures of the door ajar switch from a 1970's ford vehicle. when backyard mechanics try to troubleshoot a malfunctioning domelight, they often go looking for one of these screwed into the door jamb on late model ford vehicles.