There is a dash light that is always on when the key is on.  The panel that shows what the light is for is missing (and has been taped over).  I think the light was in the upper-right of the center gauge console.  It has both a black and also yellow wire going to the light.

My 75' is tucked away for the cold season, but if I remember correctly, not certain, it's an indicator light for the headlights. When you turn on the lights it comes on till the lights are all the way open. There are micro switches on the light opening devices, and when they are completely open it operates the micro switch to tell you they are functional and the light goes out. If your light stays on, it MAY be that the switches are missing, broken, or not functioing correctly. One of mine fell apart and created the same problem you are experiencing. They are available in most of the reputable parts catologs. Someone may be able to post a picture. They're only about and inch or so long, and as big around as a dime, and have a female plug end on them with threads to fasten them to the bracket.

 Upper right light is the door ajar light. Headlight warning is underneath it.