Help Required

Hi Folks, i am having problems with my burglar alarm-let me explain my
problem

1) on both the main control panel and the remote panel the display led
is flashing continuious which i think reads PC (power cut)
2) the alarm still sets and unsets, all the zones are working
3) had an engineer in to check the system, he replaced the battery in
the control panel, checked the continuity of the wireing,wireing OK,He
never checked the bell box, but i've still got the problem

so all suggestions appreciated also is it possible to change control
panels with a different make and keep the original bell box??

make and model of alarm system is a
Gardtec 580, with one remote panel and 4 zones

Thanks in advance