The alarm shouldn't go off if the boot is opened, there is a wire that runs from the boot lock to the alarm control unit to recognise that the boot has been opened.
So you can access the boot without disengaging the alarm.
The alarms main trigger is a voltage drop caused by opening a door or bonnet and switching on the light, thus one can open the boot but pulling the lever for the bonnet triggers the alarm as the under bonnet light is switched on. I believe in some models there is no under bonnet light but instead a switch that gives a path to earth from a circuit from the alarm ECU.
This means that if boot lid switch wire is earthed by coincidence or by error or by unwanted state, when alarm is armed alarm will go off.
Thanks for the update! Now all makes sense because I was intrigued with odd problem which was not possible to describe/diagnose in full by all we tried before.
Thanks for the update! Now all makes sense because I was intrigued with odd problem which was not possible to describe/diagnose in full by all we tried before.
Yeah, exactly. Of course, knowing my luck, now that I've posted that, it'll go off at 5:00 tomorrow morning