Just bought my third 300sd - 1985 with 73,000 miles. The previous owner stated they unhooked the security alarm by unplugging a relay under passenger side kick panel. Plugged it back in and they did the right thing. My question is when it is unplugged the relay although not honking the horn anymore still cycles since I can hear it clicking. How can I completely kill the system? Do I need to unplug a fuse, another plug somewhere?