more than likely the detector lid is not secured properly, take it back off and check the tamper spring.

Hi Norman

Will I have to power down to avoid the alarm going off before I attempt to adjust the PIR cover? Sorry but this is all new to me

What is on the display when you try to arm it?

After reading the manual from cover to cover I managed to find the section which detailed how to isolate the affected PIR, this done

The system allowed me to reset. The problem must have been the faulty case,

I have already ordered a new one.

Thanks to everyone helped

The infinite Prime is a canny beast, however the tab at the bottom of the PIR easily breaks. We have over 350 of these systems out in the field and we dread our engineers going to do a service, because they are heavy handed and break the tab. The ONLY way to get out of tamper is to purchase a new back plate. We know we have this all the time. That's why we keep spare backs. Once you have done this and the tampers (FRONT AND BACK) are defeated, press the full set button (FULL HOUSE) on the keypad. If you get a three tier raspberry noise, you still may have a fault. To check this press the down arrow button on the keypad which will show where the fault is. Otherwise your system with no faults will start setting. Simply press the unset key to stop the setting procedure.

Phil

A bit late there Alarmtek lol

over 350! I installed one and that was enough, but to be fair it still going strong ish

Hi just moved into a new property with the prime fitted got same problem here panel said battery low so changed batterys noticed a coulpe had tieraps around bottom see the little tab has gone on some other have tape all round anyway put batterys in mad sure the cases were closed put system back on but comes up with system trouble still reporting either registrtion error or battery low do i have to go into programming and reset if so how the neighbours are getting fed up have not had time to read all the manual yet so be gentle