Every now and then, and it happened last night, my Smart will flash its 4-ways as if the tailgate / hatch were left open. It's rare, but when I catch it, I just go out and make sure the doors and rear are fully closed.My alarm used to go off about once a night or more. It would also go off if it was windy which made me believe it was the motion sensor if not the ultrasonic motion sensor inside the vehicle. I figured out that if I pushed the "tow" button to deactivate the tilt sensor during towing, it would stop the spurious alarms. I used that for about a year until I drove the three and a half hours to the dealer for service.
It turned out to be a mis-adjusted microswitch on the right side of the tailgate. IT detects that the latch is properly closed. It was out of adjustment enough to intermittently make contact as if someone opened the tailgate.
The tech bent the switch lever as an adjustment which worked while at the dealer, but when I arrived home, the car wouldn't even lock. I had to undo his repair, reform the switch actuator lever, and the alarm has been perfect since. I was surprised that an alarm could be so false alarm free.
It turned out to be a known issue.
Most likely true. In another vehicle, I glued down two washers to the door sensor just to keep the factory alarm from going berserk once an hour at night. It worked by ensuring a solid contact between the door and sensor so the alarm wouldn't go crazy believing the door was opened without proper credentials (the key).I guess the struts helped keep pressure on the sensors.