The alarm system (Accenta G3) was installed a long time ago (maybe 20 years). The system was working fine until I changed the battery. (A recent power cut caused me to realise that the battery was dead). I did my research and bought a like for like battery. I installed it and when activating the alarm 2 of the 5 PIR’s come us faulty (I can see that the two PIRs in two rooms on the ground floor are not lit up). I can set the alarm by ‘omiting’ those two PIRs. I presumed I must have dislodged a wire when I had put in the new battery. I took the front off the alarm box and cannot see any loose wires.

 

Because all was good before the new battery I am presuming this is something simple but, of course, I don’t know - any ideas

 

TIA

It sounds simple as replacing the battery but often it isn't. The system charging circuit could be faulty or fuses blown. This often happens when they are not serviced regular and batteries replaced as required.

Something as old as this I would check the charging rate before and after battery replacement, but before that other checks would be done to make sure it's still fit for purpose.

It's possible a fuse has blown during your replacement but the tests above would need to be completed to check the system I wouldn't rule out needing a new panel.

Alternatively you may have faulty sensors, the new battery is faulty or disturbed some wiring in the panel but these are less likely. Best to get an alarm engineer to look at it if using a multimeter is out of your depth.

2 hours ago, Forty_Two said:

The alarm system (Accenta G3) was installed a long time ago (maybe 20 years). The system was working fine until I changed the battery. (A recent power cut caused me to realise that the battery was dead). I did my research and bought a like for like battery. I installed it and when activating the alarm 2 of the 5 PIR’s come us faulty (I can see that the two PIRs in two rooms on the ground floor are not lit up). I can set the alarm by ‘omiting’ those two PIRs. I presumed I must have dislodged a wire when I had put in the new battery. I took the front off the alarm box and cannot see any loose wires.

 

Because all was good before the new battery I am presuming this is something simple but, of course, I don’t know - any ideas

 

TIA

Something as old as this needs scrapping , I suprised you managed to make this post with such and old phone ?

 

 

Battery should be changed every 4 years, leaving it that long probably did more damage to the control panel than you would realise. A dead battery would have been pulling the charging circuit down and in turn that would have pulling everything else down including its NVM.  Its probably a waste of money buying a new battery now the panel wont be able to charge it properly. The good news is the alarm has stopped you from being burgled for no cost over 20 years, with the money you have saved you can afford to replace it