siren keep sounding off

Have a hornet alarm on my 86 Chevrolet truck, alarm was already installed when I purchased the truck, I use to think it was only keyless entry because of no siren but workin on the truck noticed a siren(Cliford siren) installed but not working aplied power to it noticed it worked, went back to the alarm brain and noticed that the siren out put wasn't connected attempt to connect the output to the siren but when I did so the siren constantly sounds not at full blast as it would if the alarm was triggered just barely but constantly and thats if the alarm is armed or disarmed it just constantly sounds, what could cause this and whats a possible solution?