Well, according to the workshop manual...
Symptom Chart
-The Autolamps are Inoperative
Condition Possible Sources Action
-Circuitry.
-Light sensor amplifier.
-Headlamp switch.
-SCIL module.
The SCIL Module is right behind the glove compartment next to the blower motor. Remove the flap under the glove compartment to allow the door to fully swing down when you depress the inner tabs that releases the glove compartment door.
Check out the picture & thread for an FYI
View attachment 828571500
Wtb 97-98 Mark Viii Headlight Module
I've also attached 2 PDFs(one on accessing the lamp switch & the other on Autolamp diagnostics) incase they help.