Hi
Its usually the back up sounder thats causes the alarm to go off
There nicad batteries inside that fail, cause voltage problems and setting the alarm off
You can replace the sounder but it needs programing
if you handy, I've split them before and replaced the battery inside for a new one, then resealed the case with polyurathane adhesive and cured the problem
Your fix above also works well, if you know someone one with jaguar IDS/SDD software they can plug in and also reprogram a new sounder or disable the sounder as well
cheers
Joe