I need some help installing some aftermarket transistor horns in m 5th gen and I just need some clarification. I think the aftermarket horn has a positive trigger and the stock maxima horn is a negative. Im trying to figure out how to wire the new horn without having to wire up another horn switch.

After reading up I understand that the pins are to be wired as followed

Pin 87: +12v from battery
Pin 86: +12v from horn switch
Pin 85: -12v to ground
Pin 30: +12v to horn

But I'm still not understanding pin 86(from the horn switch) Where do I tap this wire from? By the stock fuse box? or what?

 

Since it's a negative trigger, the diagram is the opposite of what you want. 86 should be wired to a constant source, 85 should be from the horn switch.