I have a 2000 A Class 170 CDI and have discovered a fault with the alarm.
The ultrasonics don't work (no flashing LED) and the audible siren/horn
doesn't work. The rest of the system works fine including the horn on the
steering wheel and if I open the tailgate when the system is armed the
indicators flash but no sound. I have checked the fuses under the floor and
on the side of the dashboard and they are OK. Is there a common link or two
faults? Where is the audible horn located and where does the black or red
key go if there is a problem with the whole system? I would be grateful for
any assistance from you all out there as my other research on this has so
far drawn a blank and the nearest dealer is miles away.