1990 300E Alarm sounds instead of arming itself
 

My 300E's alarm goes off(lights flash and horn honks) instead of simply arming itself whenever I try to lock the doors or trunk(happens with both the key and the door lock knobs). Has anyone seen this behavior before?

It seems to have started happening when the battery went low because of a worn regulator a few weeks back.

Thanks,
Chuck

I've had it. Still have it. It's related, in my case, to a worn key issue. I didn't want to mess with it so I finally disconnected the horn lead and I keep an eye out for the flashing lights.

Moved to Tech Help.

Answer:
 

Factory Alarm System Issues
http://www.peachparts.com/shopforum/diesel-discussion/150748-factory-alarm-system-issues-post1143583.html