the touch lock button on the door handle
 

is it thermal based? recently I can't touch lock the car a few times I guess it was because my fingers were too cold. I tried today and it was no problem.

Must be some type of conductive surface, because if you wash the car with the key in your pocket it will unlock the doors constantly.

If it was, would it work when the ambient temperature equals body temperature?

Yea, I have noticed both of these phenomenon

When it is super cold out sometimes it does not lock from my finger and I have to use the button on the key fob

And washing the car with the key in the pocket is the worse. It locks and unlocks constantly even if I am not over the door handle

After 11 months with my '13 PP+ I have recently learned to keep my finger on the button until the cars locks. Just touching it usually resulted in my having to touch it again. Now, even with gloves on, I just put a little pressure on the button and wait 2 or 3 seconds and the car locks every time.

It might be pressure based instead of thermal based. . I'll try push next time.

Once it was so bad I tried all four doors without success. Lock on the key fob didn't work as well. Had to use the mechanical key to lock the car.

It definitely is not pressure based. I often never touch it to lock it. Just have my finger close to it. Plus the car washing phenomenon as well - my hand usually is not close to the door handle and it will lock or unlock while washing the car if I have my key in my pocket

They might be capacitive door handles. My old 06 Acura RL had similar door handles, and they behaved similarly to the A6 door handles in cold weather and in car washing situations with the fob in your pocket.

I concur, most likely conductive. Conductivity can change with the weather as well which is why it can be more and less receptive.

They actually do use capacitive sensors.

http://www.audi-portal.com/en/diagno...ors_17395.html