seat belt buzzer issue

I have a 72 Swinger. I unplugged the wires under the seat years ago for the seat belt buzzer. Now the buzzer and the light on the dash come on while I'm driving. It's very annoying. Sometimes they come on when I hit a bump or go around a turn. It usually goes right back off but on other occasions it will buzz for 15 minutes or more until I hit the right bounce or turn and it will go off. I'm hoping someone has some idea of how to correct this.
Thanks,
Frank