holy crap!!!!!!!! i did that once to a " friend" as a joke in highschool. there is a switch just off the left side by the brake pedal. it has 12v constant power power all the time. the horn leads come out of the steering column harness and go through the firewall to the parkinglight/ horn harness. all you have to do is tap the brake wire to the lead wire for the horn. basically the switches for both systems complete the ground as they have power all the time, and only ground out when the horn or pedal is actuated. this is so cool to see this in a video!!!! LMAO!