2002 A6 Avant...I think my driver side door latch may be the problem. The car doesn't seem to know when the door is opened (the interior light doesn't come on unless I open one of the other doors) I can lock the car with the key, and the window up and down feature works with the key, but the remote doesn't do it any more. Also, if I lock the car and it is sitting in the sun, the alarm will start going off in a few minutes. This doesn't seem to happen at night, or if it is cold outside. Has anyone fixed this problem?

 

I have a 2003 A4 Cabriolet and I am having a similar experience. My remote isn't working and when I lock the car with the key, the alarm will go off for 45 seconds and then stop. It happens every time, no matter if it is in my parking garage at work or in the sun. I am taking it in to the dealership on Saturday. I will let you know what I find out. I was thinking it had to do with the remote not working, but maybe not.

 

@ OP, I'm sure your door switch is bad, it is a common problem. Are any of your windows or sunroof open when the alarm is going off?