my accenta g3 optima keeps going off randomly for no reason ?

Hi
I have moved into a new house recently and my alarm has randomly gone off for no reason , i have not used the alarm since i have moved in as i didnt have the code , i have called a engineer out who has reset the system so i have a code, but the alarm still went off at 5am when i tried to reset it it was accepting the code but still keep going off ! i called the engineer who told me to put the engineers code ( prog 9999) an it has not gone off since but i have a permanent tamper fault light on . Any ideas as the engineer cant come back for another 2 weeks !!