Air Horn Relay

use the relay.  The air horn may sound using the power from the horn, but it wont be as loud as if the airhorns compressor has its own power source. and it wont blow ahorn fues either if you do it that way.

I second that, Do it right the first time. The relay will save you troubleshooting time in the long run.

Where do I hook up 86 and 85 too? I know 30 goes straight to the battery and 87 goes to the compressor. I got an Integra 92, and was told when i push the horn button then it becomes grounded, does it make a difference?

If you want to use your existing horn button and the button(switch)  is on the (-) side of the circuit, connect 85 to the horn wire .  Connect 86 to a constant 12vdc source.    (If the horn goes off constantly when you hook it up without pushing the horn button you are on the wrong side of the horn switch.) 

If you want to use a seperate button. ill find that diagram.

I threw this together dont mind the trial software stamp.   If you do this one make sure you fuse it near the power source.