MNKYBZNZ

This has happened twice now: First, I was backing in a trailer at work, I work at a warehouse, and move 48 and 53' trailers quite often. First time, I bumped the dock kinda hard. (I mostly move 48' trailers and this one was a 53', CRS moment) Second time I was walking by my car, with the windows cracked open since it was hot outside, and tossed in a letter I got from a coworker. Both times, it was like I hit the panic button on the key. Horn blew so many times, then the lights just flashed until I got my key and hot the unlock button. Is this something Ford installed, or could there be an aftermarket alarm I don't know about, or is this some goofy coincidence. I know coworkers weren't doing it playing tricks on me.

JimC

You have a motion sensor inside. Look up at the light on the headliner, and the two openings on each side are the sensors. When you lock the car it arms the system. Tossing something in the open window will set off the sensors.

MNKYBZNZ

Thanks, I appreciate it! For some odd reason, the previous owner decided to keep my manual, and the new one hasn't got here yet!!!

JimC

You're welcome. Not every Mustang will have the alarm system, but as soon as I read what you wrote I recognized the events. There are motion sensors on your car and various other sensors.

There is one under the hood (passenger side near the fuse box, looks like a plunger) that is the most exposed to elements. It can go bad. It is there to sense if the hood is open. When it goes bad it will trigger the alarm because it is defaulting to the hood being opened. Easy to replace when it happens.