Might be silly... But where is it? I've checked every control and just can't find it. The light controls go from off, to drl, to high. The turn signal stalk doesn't go forward or back and there are no other light controls I can find.
The 1980 Eagles were the only ones with the old school, floor mounted switches that are foot operated. It might be hiding under the floor mat or carpet. Good luck!
Thanks @vangremlin! I'll keep hunting to see where that beastie's hiding while I'm replacing the forward parking brake cable.