how to blow car horn with alarm

i have a audiovox prestige750 plus that i want to hook up horn blow to it it doesnt have horn output i tried to use the diagram on this website for light flash with siren output it works to a certain point it blows the horn but only if when the alarm is going off i have to disconect the ground wire then reconnect it it blows then if i turn it off it wont blow till i disconnect the ground again i am stumped oh and i checked the voltage at the siren+ wire it is 12.09 to11.98 when the alarm is going off is there another way to hook this up please help

So let me get this straight, you want the horn to honk when you arm and disarm the car, or when the alarm is going off?Kyle@Audio Obsession Sound

i would like it to to both if i could when i disarm and when i arm

Use 2 relays; one relay hook up park lights to pin 85, ground to 87, out put(30) to horn, and 86 to output of second relay.  Config. for second relay is as follows:  85 and and 87 are tied to ground, and pin 86 is attached to your siren output.  Pin 30 is hooked up to pin 86 of the first relay.  This setup will let you hear your siren and horn chirp when you arm and disarm, as well will give a pulsed output when the alarm goes off because it goes with the timing of your parklights.  Good luck and let me know if this works for you.Kyle@Audio Obsession Sound