Need help with a lighting issue

[Andy_M]

I have a '90 300E that keeps blowing fuse #3 which is for the dash lights, controls lights, right side parking lights, and headlight wiper motors. The first time it blew was at night about 1/2 way between work and home. I replaced the 8amp fuse and it was ok for a couple of days before it blew again. Once again at night on the way home. Since then, when I replace the fuse, it blows as soon as the parking lights are turned on. When it blows I lose dash and console lights, right side parking lights, and the door buzzer.

The wiring diagram would seem to indicate this is most likely one of three things: 1) Light switch; 2) Headlight wiper relay; 3) lighting control relay (the $180 baby). The problem is that I can't find a listing anywhere for a "headlight wiper relay" so I don't know if this is actually the interior light relay (which apparently works fine) or the

I'm thinking it is most likely the light switch. Opinions ? Other ideas ?