Hi,
Before you spend days doing what is a few hours work... most DIY don't understand the basic operation of an alarm
The alarm is working 24hrs a day, think of its as 12 & 24hr circuits
24hr, tamper circuits, in detectors, controls, keypads, bell ect.. these work all the time
12hr circuits, motion sensors & door contacts ect.. these work when you set the system
For example should the tamper on the external siren operate when the system is unset, it will ring externally regardless of programming & the internal speaker will operate to alert you of tamper condition.
To change your alarm over is 1 days work, to fault find your existing, replacing all batteries & external sounder 1/2 day.