Ok here's one for ya: clearance lamps turned themselves on when the switch is off

Need to pull your fuse panel back and see if it has corrosion on backside. If it's not to bad you can clean and rewire. Did one in a 98 w900 was so corroded you turn the ac on the lights would go out.

 

Hummm... looks bullet switches... the small brass/copper guts and springs and ball will sooner will wear out.
If they are the same old switch I think it may be, you may be able to careful take it appart and fix it. You will have to relube the switch guts.

 

Everything was installed backwards.

Turn it around

 

Had a similar problem with the headlight switch on my '05, the insulator(plug) had got hot enough to soften up the plastic and allowed two of the wires to touch inside the insulator. Unplug the switch and wiggle the wires inside the insulator, they should not move at all. Check the lights while you are moving the wires in the insulator see if they are lighting.