Got a call today from the campus police. Apparently my car horn had been blaring incessantly for a while, and they thought it was an alarm. I'm glad they called because my office is the better part of a mile from the parking lot, so there's no way I'd hear it. It was still going by the time I got down there. I still have no idea what's causing this, so I just had to yank the fuse to get it to shut up. Looks like it's more complicated than just condensation or it should have dried out by now. I'll have to take it in for service after all. Of course its too late to call the dealership now, and they won't have any mechanics in until Monday. And the nearest dealership is in Salinas.