Chrysler Repair: 96 Explorer, electrical warning inop, ford explorer xlt, thumb wheel

Question
I have a 1996 ford explorer XLT with a 4.0 engine, and 4wd. My problem is electrical in nature. I've noticed that the interior light does not come on when the door is opened, even though it will still work with the thumb wheel on the dash. The warning buzzer that indicates that I have left the keys in the ignition, and the buzzer for the headlights left on does not work, and the fog lights do not work. I'm not sure if this is a complete list of malfunctions or not. So far, that is all I can find wrong. Is there a common thread to all these problems? A fuse(I've read the manual and checked the appropriate fuses, which are ok)? or maybe a relay somewhere?
Thanks in advance!

Answer
It sounds like you've just got a simple door ajar switch bad.  I'm not real familiar with explorers YET but on the chrysler products there's frequently a single wire going to the switch.  The door is opened and a ground path is completed through this switch to the vehicle's chassis.  This switch can frequently not move far enough to complete the path to ground, the screw that holds the switch in place (which is a grounding screw) may be corroded too much, the mating surface is corroded too much, or simply the switch has completely failed.

Everything that you've described thus far is related to a door ajar type warning.
Doug