The factory alarm in my friend's 1997 Explorer randomly goes off... She has figured out how to not arm it when leaving the car (manually locking it), but when she forgets or others drive the car, it gets armed... and then goes off randomly on its own. How do I disable the alarm without losing function of the remotes and keypad entry?
You either need to replace the box (it is in the back on the driver's side) or find the fault that is making the box think it is being broken into. Don't rule out the panic button on the key fob as a problem source.
Also, these systems are sensitive to RF sources. Here in Las Vegas, the emergency radio system jams them or makes them go haywire (a repeater was stuck on once). Other devices like wireless routers could potentially cause problems, although not as likely as something that puts out a lot of power. My remote won't work at a neighborhood Blockbuster. Perhaps it is the device that prevents theft there. Those work by sending out RF which talks to an RFID sensor in the case. The point is, there could be many sources.