Air Horn on Delay through factory horn

hello all, i have new truck and had some air horns laying around and hooked them up. rather than plumb a wire for the switch, i was thinking about another solution. i really only want to use the air horns in extreme situations, such as laying on the stock horn for 2+ sec. this would allow me to be obnoxious when i needed to, and not bother many people for a simple beep-beep. i have no details on my specific China air compressor other than 12v 20amp (i think) as it didnt have directions. currently I have it wired for negative trigger with the relay & switch under the hood and it works fine by itself. what i am thinking of doing is taping the factory horn voltage and using a capacitor to atain my desired 2sec delay for my compressor. I have a handful of caps, but thought i would ask before i start to experiment. has anyone done anything like this? any advise would be greatly appreciated. hack6500

Check out this prior post on airhorns, looks pretty close to what you're trying to do-