Quick electrical question
 

I just finished running the wires for my new air horn. I grounded it to the chassis and ran the wires to the cabin mounted switch. my question is this, where would be a good place to tie the positive wire into? Either 12v always or 12v when the key is turned to ACC and where? Where have you guys tied into if you have put another horn in?

I'd put it in how the Germans would: put it in parallel with the stock horns, but add a relay with a selector switch in the cabin so that you can choose which horn honks with the button.

I thought about that but I want to keep the original horn how it is and have the air horn on its own. Mabye the positive for the power seat since it is easy to get to?

Chances are you won't be adjusting the seat and blowing the horn at the same time, sounds good to me.

Domestic cars typically have the horn on a non-switched supply, European cars usually on a switched supply, same with cig. lighters, could use that power.

It really doesn't matter whether you go switched or constant power, factory provides a constant source. The important thing is that whatever you tie into, make sure either it has a fuse already upstream or put a fuse on the horn wire at your tie in point. Do NOT upsize an existing fuse! If you go with an existing prefused line, you will know quickly if it will or won't sustain it, either the fuse will pop from too much draw when you turn everything on in that circuit and hit the horn, or it will work. If you are really worried about too much load, you can put a relay coil into the existing circuit switched by your button of choice, and then run a new devoted fused circuit thru the relay contacts to the horn itself, this separates the horn load and provides for minimal draw on the existing circuit. You can put the relay under the hood with the horn to minimize the extra wire run.