Just out of curiosity, how well do your wipers park when you turn the switch off? I think the horm and the wiper park circuit share the same power source. I'm using the 87 montero manual, because the only MM manual on Bill's web site is the sorry haynes toilet paper manual and it doesn't mention the horn at all that I can find.

You should have two fusible links, one right at the battery, a bid fat one, and one somewhere else under the hood. Mitsu either likes to put them in a black plastic box beside the battery or on the fender somewhere.

Not responsible for advice not taken...