3 is our dinning room.

It it worth checking to see if the wiring to alarm panel is ok and that the sensor is ok. Or possibly try swaping\changing the sensor.

I will now assume you mean a movement detector of some sort in the Dining Room.

Have you done any decorating in this area? Quite often a decorator will remove/replace a detector when wallpapering and sometimes the tamper switch to the detector will be broken, cover not replaced correctly, tamper spring lost etc.

Unless what I've suggested turns out to be wrong, the next thing to look at would be the cable between the detector and the panel but that's for another day. (new carpet fitted upstairs, cable damaged?)

Good luck

thanks magpie.

Just moved in not long ago so don't know the history. Will have a play around with the IR sensor.

Will post back if I need more info.

Thanks for all the invaluable info

why dont you just link the tamper circuit out on zone 3, you never know may just be a fault on the pcb. If youve got a meter the check the resistance on the tamper circuit, oh just to let you know the alarm circuits are on the left the tamper on the right for each circuit