Alarm woes.. Optima XM...possible PIR fault?

This has been driving me mad for a while... the first time it happened was in the middle of the night. There was a loud high pitched tone, a bit like a fire alarm "I’m running low on bat" noise but slightly longer and louder... scared the bajesus out of me! The noise went off every now and then, like said smoke alarm warning.

I went to investigate - thinking it’s just a bat in one of the smoke alarms... the noise stopped... went back to bed it started again until I got out of bed to investigate, and it stopped again... this went on a few times each time having the same result. I decided to pull the bat from the smoke alarm (don’t worry, we have another in roughly the same area – but I know it’s not ideal…) and went back to bed.... ARGH it went off again. I put the battery back in and pushed the test button - different pitch noise. I tested the 2nd alarm - different pitch again.

Only conclusion I could come up with is the PIR for the alarm system was making the noise and when it detected me it caused what ever fault to stop – but I thought they did not come equipped with sirens. I set, then unset the alarm and fell asleep. By the morning, the noise had stopped, not sure if it carried on after falling asleep…

It has been around 7 months since then, and tonight it sounded again, twice, I went to investigate and it stopped... and it has not sounded since.

There are no errors showing on the panel, and as already mentioned - it seems to be mocking me by stopping when i go to investigate! The alarm is an Optima XM with 3 PIRs and one door entry system. I suspect its zone 4 (landing PIR which I suspect is making the noise). No idea how old the system is, but it looks as though it may have been fitted at the time, or close to the house been built in the early 90’s. Unknown service history nor have we had it looked at in the 2 and a half years living here.
Just taken a look through the manual – nothing about it in there either.

Any thoughts before I take a lump hammer to the alarm control box!

Won`t be the PIR thats for sure.

I thought that, but with the oddness that we had that night, its the only other thing it could be! And with it stopping as soon as I go to investigate, triggering the pir....
Saying that the siren in the control box is quite loud so I suppose it could be an odd effect with sound up into that area...

I have found some instructions on how to run a few tests so going to try the walk through test tonight

Other than that, the alarm has always behaved itself, no false alarms, been ok during power cuts, no errors or tamper warnings.....

~When was the standby battery last changed?

Standby bat has not been replaced since we moved in 2.5 years ago and we have no history to show maintenance or replacement parts before we moved in.

I was thinking of replacing it as I know UPS for computers can have issues when they age, but wanted to see if it could be another fault first....

Alarm said:

Won`t be the PIR thats for sure.

Click to expand...

That's for sure, it's a dead certainty, there is nothing in a PIR to make a noise.

Unless you can hear a relay clicking that is.

ok, so after a good google session, I didnt really get much of an answer, and looking at battery prices they looks quite cheap and worth throwing a few quid at to see if it fixes it..

Anybody know what size I will need... from the instructions it says 12v 1.2aH to 6ah but does not mention the dimensions...?

Damn cannot remember.
Think it will take a 7AH.
Check the old one

Actually think it was a 2.8!

this seems to come up a lot
https://www.batterymasters.co.uk/Pr...ttery-(L(mm)-W(mm)-H(mm)-134-67-64)_1755.aspx

if replacing the bat does not solve it, im taking the lump hammer to it and replacing it. I suspect its easily 15 year old at least and they seem to have a reputation of burning out the bat charger, or having controler chip issues!