Headlight mechanism

There is a limit switch on both ends of the headlight bar. One sets the limit for 'up' the other sets the limit for 'down'. Take a close look at the left side of the area, just behind the radiator. Note the headlight "uppy-downy" motor turns a gear that runs the bracket (for the lack of the correct term for this part), which is connected to the headlight bar/assembly.
This bracket physically touches one switch at either end of it's travel.
It may be likely that the limit switch just needs cleaning.

You can contact me directly at Melton01@msn.com
I have images of these parts....

Chuck

If its not the down-limit switch, it sometimes is due to a dead commutator bar in the DC motor, positioned so that the buckets won't travel quite all the way up or down. Replacement Ducellier motors are not easy to come by except from the major Pantera parts vendors, so hopefully its simply a slipped switch.