The built-in security system on my car is malfunctioning and goes off whenever it feels like it. In addition, my blower fan keeps going bad. I have had to replace it twice, but it keeps freezing up until it won't work at all.
Your security system is likely controlled by a control module or computer of some kind. Considering that you say the alarm has a mind of its own, this may be a computer issue and will likely require scan tools for diagnosis. As for the blower motor, if the blower motor resistor was not replaced when the motor was replaced, this could cause your issue. It is also possible that you have a short circuit somewhere via exposed wiring in the blower motor circuit which is causing the fuse to blow and therefore makes the motor inoperative. A full inspection of both systems performed by a qualified professional should lead you to the correct diagnosis of both of your issues.