Intermittent Alarm Sounding When Vehicle Locked

As stated in the title I've noticed the alarm and indicators flashing for no reason when parked outside my front door. In the past I have assumed a fly had set off the perimetric alarm while the sunroof was open.

Unfortunately this seems to be wishful thinking. I reset on the fob, only for the thing to sound off again almost immediately. Left unlocked, unlocking cancels the alarm, she rearms herself after a while and problem temporarily cured.

I seem to recollect a post referring to the very same problem and talking about a flat secondary battery in the alarm itself. Is this eyewash as everything on my CLK is very dead once the battery is disconnected.

Anybody got any idea's?

cheers

 

You will be needing a new siren sir, the batteries have expired

 

Thanks Malc, is this diy or does STAR deed to reconfigure everything?

 

Plug and play about £80 from MB, nothing to set. you can just unplug the alarm siren if you wish and leave it at that