Anti-theft system (ATA) - C Class

[microkid]

Does anyone know how to activate the interior motion sensor for the factory fitted anti-theft alarm system (ATA) on a C Class? The passenger window on my coupe was recently smashed, however the alarm failed to sound, and currently the light on the interior sensor button does not flash, only the tow-away protection one.

 

[seymansey]

It should be activated by default with the option of you being able to disable it when leaving the car. Either there is a fault somewhere or perhaps a previous owner wanted it to be disabled by default which IIRC can be done via STAR (maybe they carried a dog in the car about a lot?)