disco alarm

hello,
been having a bit of trouble with my alarm going off all the time, it sometimes can go weeks with it not going off then all of a sudden it will go off all the time -upto every 10mins most of the night! then after a day or two quiet again. anyone any ideas of what it might be?

Which disco is it
my 300tdi used to be like that when it rained as there was a leak around the screen which let water get into the alarm wiring. If i locked it with the key instead of the fob it was ok it never went off but by doing it this way you disable the interior alarm sensors so be carefull especiialy if you live in a dodgy area

how long have you had it is it a blue one might be my old one

its a 98 300, (met green) i aint noticed any wet around the window but i will check it out when i do the rear sunroof tomorrow. is the immobiliser still on when i just lock it manually

yes it does get imobilised
try feeling in the drivers footwell for damp thats where mine was