Alarm and Infrared sensors

I've searched and didn't find what I was looking for, please forgive me if this has been done over and over. Anyway, after reading the manual on the alarm system and the infrared sensors on the headliner console/rear view mirror...it's still not clear to me how it's really supposed to work. The manual seems to indicate that the infrared sensors should detect movement on the front hood latch, engine compartment and door handle area's......but I can't seem to get the alarm to trigger by moving about or acting as though I'm trying to access those area's? Or, I'm I reading it wrong and the IR sensors only monitor interior area's....like if you wanted to leave the sun roof open or the windows down and someone were to stick their hand in or try to climb in? Or, Is my alarm screwed up and not working properly. Any enlightenment for this newb would be greatly appreciated. Thank you.

Motion sensor (on US cars) monitors inside of car only. It is active when alarm is set by locking with remote. When top is down on the cab, it is not active. Try it: get out and leave your wife/kid/dog in the car. Use your remote to lock the doors. At their first movement, it will sound.

Yup, just lock yourself in the car with the remote. Move around and the alarm goes off. If you are waiting in your car and want to lock the doors, use the door lock buttom on the console, not the remote. Or else, you better sit still.

Thanks for the replys, the manual was a bit confusing, at least to me. I was thinking, why in world would anything be moving in my car after I lock it......but I guess it's in case you leave the sun roof open. Thanks again

I have locked my car with the sunroof open and a cat jumped in. Which , did set the alarm off. The cat was difficult to get out, he was scared to death by the alarm, luckily he did not get the S%&t scared out of him.

Or, in case someone breaks a window and reaches in .... or cuts your Cab top and reaches in .... This feature even allows you to lock the car while leaving the windows down (in the hot summer while you run into Starbucks), and still have the inside of the car monitored for anyone reaching in or messing with it. (of course, I wouldn't recommend leaving your wallet on the seat under these circumstances).

Never thought of protection when leaving the window down... If that's the case, why can't the alarm activate with the top down? I leave the top down and windows up sometimes for short stops. I suppose some leaf can trigger the alarm but the IR sensor isn't that sensitive. I sat in the car once w alarm on and moved very slowly, alarm didn't go off.

This is an old thread but helpful, so I though I'd share. My 2002 996 Cab beeps twice when I lock it with the fob (manual says "a double horn signal during locking indicates a fault in the passenger compartment monitor ie the infrared emitter). After I leave the car parked for a while, the alarm will randomly go off. Drove me crazy! Finally found that if I click the remote twice the car will lock, then unlock. If I leave it like that without opening the doors, it will relock in about a minute with the infared disabled. Eureka!....no more false alarms. Hope this helps someone. Bob