New to this forum and need help with a problem I haven't seen addressed here. Over 5 years ago I bought a used 1999 Deville Concours and just recently started having some incidents with the security system. My owners manual doesn't mention it either. I know when the security system is set off, the horn will beep and lights go on and off intermittently for 30 seconds. But twice lately I've had a situation where for some reason the horn will start blowing and blow continuosly. The first time someone disconnected the horn for me as a quick fix, then had to hook it back up later. The second time it went off I got in the car with my key and hit the steering column hard, where you press to honk, and that stopped it. Both times this happened early in the morning (still dark) and woke up several of my neighbors, who are a little po'd at me (but hey, it isn't my fault). I called a local Cadillac dealer's service department and they told me the only reason the horn would go off continously like that was if someone tried to get in the car without a proper key. Do you think it's more possible someone was trying to break into my car, or maybe a short or something else? This has never happened until a couple of weeks ago (at the same time there were several car and house burglaries in my neighborhood). It doesn't happen when I'm driving it, or otherwise near it, and only late at night. A couple of people are insisting it's the weather conditions causing it to go off, but the weather here hasn't been any different than usual. Anyone know if this model has a tendency to have this kind of horn problem? Any mechanic that can do it wants an arm and a leg to analyze it, which I can't afford now, and my only other choice might be to set up a security camera to see if someone is tampering with it. Any suggestions are appreciated. Thanks.