hey mate, im 3rd year auto elec, in my experience alarms are a bastard, not to fault find, but they are just not that reliable and most of them are installed horribly! There is not much to a basic alarm system, should just have a 12v supply, earth, door lock signals and your start supply to starter motor, fuel pump or coils or all three! As long as you have these into the unit, than your alarm module is no good, and this is most likely! it will probably be cheaper and easier to just get a new alarm installed!