Just thought I would bring this topic back as it was discussed a while back and people said that the alarm does not have its own battery.

I had some time on WIS and looked it up. The alarm speaker does have a battery on the W203. It also has a micro controller built into it that sounds the alarm if it detects a loss of power or communication. It is smart enough to not go off if the power loss is from a dead / dying battery. The document is GF80.50-p-4110q and it says it is for model 203.0/2/7 with code 551 anti-theft alarm system. It's referred to as "alarm signal horn with additional battery".

Heres an idea: someone (mid city engineering, you listening?) should create a shock sensor that can be mounted behind the trunk liner and plugs into the can bus to send an alarm message to the rear SAM when it trips.

 

Yes - I pointed this out to Moviela - what I did not know was where it was until some recent posts by members - It comes up as a serviceable item in SA