Well this is too stupid for words. There was no fuse in the fuse holder, but the LIGHT on the holder came on consistently, so I never even thought to look. I figured if there was ONE wire that was right, it was the one from terminal 30 to the battery. I KNEW it was going to turn out to be something ridiculously simple...
After making a wiring change, the light stopped working and I thought I might have blown the fuse, checked and found.... nothing. Why was the light coming on if there was no fuse?
So now I need to know what size fuse belongs in the holder. I can find no clue with my instructions (which also don't tell me to install a fuse as part of the install).
Thanks for the diagram. I understand the circuit a little better at the very least, and the diagram would have been easier to follow than the poorly written instructions. BTW, though, my instructions didn't call for a wire from the (-) side of the original horn wire, and the horn works without it. Don't know why...