Car Alarms: Grimlin infested alarm system on 93 Bonneville, alarmtek, pontiac bonneville

Question
My 1993 Pontiac Bonneville's alarm system has been going off by itself.  One time it went off when we were stitting in the parked car, (engine was off). When we opened the hood, the alarm stopped. Another time we were driving the car and "wham", the alarm started up again.  We pulled over, turned the car off, opened the hood, waited and about 10 minutes later, it turned off.  We took it to the local dealer and they searched for over 7 hours and couldn't find the system to disable it.  HELP, the car is probably worth $200 max, I don't think we need the alarm system at this point.  How do we disable it?

Answer
Please be more specific.

I need to determine whether it's a factory alarm
issue or, if it's an aftermarket system you are
dealing with.

Is it: Headlights flashing, car horn honking
and a worded SECURITY" light in the dash flashing?
(doubtfull since none of the notes show this
car as having a factory alarm system)=FACTORY

Or,

is it: flashing parking lights,
an LED in the dash area, and a siren
going off?= AFTER MARKET

Let me know more on this to better
advise you on a course of action
to take.

Best Regards,

Robert Martin
CEO/ALARMTEK
CARALARMMAN.com