I have a 2003 A4 Avant and, as of late, I've had a number of electrical issues: water-logged alarm siren (replaced at the dealership for an arm and a leg), an old amp with corroded connectors that drained power like crazy (junked it and ordered another one on eBay), and finally, this week, the rear lights that come on and stay on, draining the battery.

A neighbour left a note for me that my lights were on, and I looked at the switch and it was in the "0" position. I called the guy and he said the REAR lights were on. I was like WTF?! How can that be on a powered down and locked car? I thought it was the stereo bullshit again, so I pulled the fuse for the stereo, but, sure enough, this morning I found the car with the rear lights on and the battery almost drained (I could still lock/unlock the car, but not start it).

Now, could anyone please look at this photo and confirm for me that these are indeed the brake lights? I assume they are, because the light on the hatch is also on. What the hell could be causing this?

 

check for a faulty, or poorly adjusted, brake light switch in the pedal cluster.

 

THIS^^^ and if you can DIY the switch from the dealer is usually about 10 bucks and takes 5 minutes to change.

 

Well, since I don't really know what I'm doing, I went to the dealer and got them to look at the issue. They said I had an "old-style" brake switch installed, so I got the "new-style" one installed instead. Considering it cost me just $109.76 including labour and taxes, I think I got a good deal...provided the car starts tomorrow.

 

Yep. The car works perfectly now. The old brake switch was the issue.