Is your motion sensor too sensitive?
 

When I purchased my CS one year ago I could stand beside my car with the window down and not set off the alarm until I put my hand through the window opening which is the way I believe it should function. A few months a go my mechanic fixed a short in my electrochromic mirrror -- the wiring being where the sensor is housed -- and since then when someone passes the open window within three feet of the car off goes the alarm. This leads to my question, is there a sensitivity switch for the motion sensor? My mechanic didn't even believe I had one until I showed the manual. Now the manual does say the windows must be up to prevent this sort of incidence but that does not answer the question. My mechanic promised to check into it but so far is playing cat and mouse and nowbody else offered an opinion. I know that Mercedes motion sensors do have a such switches so it's not unheard of.
Any help would be appreciated that I can take back to the dealership. Thanks.

All smiles all the time with a GT/CS (yup still smiling)

I don't recall there being any adjustment. I agree there should be a valet mode or something for those of us who have this feature. I have to keep the keys in the car when I am working on it at night, nothing like the alarm going off at 2 AM in the house. LOL

You can set the alarm without using the sensors by using the key in the door to lock the driver side door. Just lock the other side by hand or whatever. If you do that, the alarm is still active, but the motion sensor and tilt sensors are not active. It still monitors the doors/trunk/hood.