There are two vibrator-type horns on the H2, and vibrator horns can possibly - if not adjusted correctly draw a lot more current than they should. What you might do is disconnect one (it should be a simple plug on the horn itself) and lay on that single horn (sure hope you have understanding neighbors
), to see if the fuse blows. If not, then replug it and then unplug the other. Do the same test again.
With the one that blows the fuse, you might be able to adjust it so that it draws less current. See if there is a screwdriver adjusting point on the side. If not, then you could just replace it (two horns, one is the "hi note" the other being the "low note").
If you can prove the horn blows the fuse, you should be able to get it replaced under warranty; if not then, good replacement OEM-like (or even louder) horns should about $15.