I have a 98 Avenger with no installed security system. A couple of days ago, the panic horn started sounding out of nowhere. It will start sounding at any time, for three minutes and then stop, even while driving. I took the batteries out of the key fob, thinking something might be wrong with it, but the horn still went off. I also took the alarm fuse out of the fusebox, but that didn't work either. Does anyone have any idea what the cause of this problem is?

 

try the door pins. mine went off, but not while i was driving. they look like little plugs on the inside of the door thats connected to your car. some people have cleaned them, some have replaced them, as i did.

 

With the alarm fuse OUT I doubt it's the pin switches ...
I'd guess the relay may be bad ...