[ANovak]

Speculation on how the Comfort Access works to lock and unlock the doors seems to consist of the following two theories.

A Pressure sensors in the front door handles. Pull on the door handle to unlock and push on the pad on top of the door handle to lock. To explain the fact that the car locks and unlocks when spraying the door with water while washing, water pressure is used as the driving force. This does not explain the fact that you do not need to apply any pressure to lock or unlock the car. Just placing your hand between the door handle and the side of the car (without touching either) will unlock the car. Holding your finger above the pad on the door will lock the car.

B. Magnetic field generated by loops in the front door handles. Claiming this works like traffic light loop sensors in the asphalt that are activated by cars pulling up to a light. These sensors require an object in proximity to the sensor that has magnetic properties (iron, nickel, cobalt, etc.). The human body and tap water do not have enough magnetic material in them to disrupt a magnetic field.

Here is my theory on how the Comfort Access option functions.

C. Capacitance proximity sensors in the front door handles. These sensors work by detecting a change in the dielectric constant of the material in front of the sensor. The dielectric constant of air is 1 and that of water is 80. Since the human body is mostly water, the sensor can be set to detect the presence of water displacing the air in front of the sensor. This explains the effect we see when washing the car. Water is detected by both sensors, thus the car locks and unlocks in rapid successive cycles.

To unlock the car, I place my hand around the door handle without pulling until I hear the click of th car unlocking and then pull to open the door. If you start pulling before the car unlocks, you need to release the door handle and pull it again to open the door.

[BK]

If I just stick my fingers between the door and the handle without touching anything, it unlocks. I usually throw my briefcase behind the front seat in the mornings, so I have CA set to unlock all doors. When I walk up to my car in the morning, I wave my hand behind the front handle then can grab and open the back door in stride... it feels sort of like setting off a motion sensor in front of a grocery store automatic door.

However it works, it works perfectly for me so far, and I am glad I got it.

[ppejack]

I'm looking forward to getting my 335i with CA so I can experiment with it.

[KevinC]

Wrong on all counts. It's RFID technology, which is a lot more common and has been around a lot longer than most people realize.

[BK]

I nearly left the keys in our other car today when I got out. I am so used to just shutting off the car and stepping out without grabbing my keys.

[ANovak]

Originally Posted by KevinC

Wrong on all counts. It's RFID technology, which is a lot more common and has been around a lot longer than most people realize.

RFID has nothing to do with sensing if the doors are to be locked or unlocked. Identification of the key fob that is known by the car is RFID's purpose. If there is a valid key fob near the car (within 6 feet in my experience), the electronics in the car enables the door sensors.