Why do the door chimes on my Ford Explorer no longer work when I leave my headlights on?

A while back I noticed that the door chimes no longer signal to me that my headlights are on when I open the door. Not just that, but neither my cabin dome light nor car door light comes on when the driver door is opened. (When the penger door and other doors are opened/closed, those indicators work fine). It's like my car no longer knows when my driver side door is ajar.