So I just realized this evening that some of the interior lighting on my '90 535i doesn't seem to be working properly. When I turn off the car, all the lights turn off, as normal... EXCEPT the backlight for the power window switches. It stays on for a period of time, and I can still run the windows/sunroof open/closed. Eventually the light fades to off and I can no longer move the windows.

I realize this is probably some electrical gremlin that I'll be chasing for a while, but I figured I'd see if anyone had any ideas on a place to start looking. Do the interior wiring harnesses rot on these cars?