As the alarm went off during power cuts I replaced the back-up battery- the old one was definitely jiggered. However the problem persists. Any ideas what is causing this?

Did you check that the charging circuit was o.k. before addind new battery?.

Is the battery sufficient to support your system in a power cut ?.

Does the alarm trigger immeadiatly that mains power is removed ?

Your system is quite old , so the charging circuit may be fried if it still had the original battery.

Check the battery fuse?

Just tryin to help matey...

As the alarm went off during power cuts I replaced the back-up battery- the old one was definitely jiggered. However the problem persists. Any ideas what is causing this?

Thanks for the help guys- the fuse wasn't actually making contact with the clasp. It has probably never worked. I have just bought the house and the fellow who had it before was a sparky so he probably installed it himself....Many thanks