If you're lights are flashing but no sound then I would guess you're alarm is working,but the Horn/siren is disconnected.
My alarm on my '85 380se would go off in the middle of the night every once in a while,even though I never used the red dotted Key?.Yesterday,I finally disconnected the closest connector to the floor behind the passenger foot rest panel.Everything seems fine now.I dont need an alarm anyway.



'85 300se
'81 240d
(girlfriends '82 300TD Turbo)