A strange problem.... my battery dies when the trunk of my 2007 A4 cab is left open for more than half an hour.
It's not the trunk light (I disconnected it).
And it only happens when the trunk is left open - otherwise, the car runs fine and there's no problem starting it.
I'm a scuba diver, so when I'm diving I leave my trunk open while I'm sorting my gear.
It's clear that something is draining the power very quickly - but only when the trunk is open.
One other factor - the actuator for the trunk lock is broken (no sound at all when I try to actiivate it with either fob or door-mounted toggle).
I'm not sure if the two things started at the same time and are related or if it's just coincidence.
Any thoughts?

 

How are you opening the truck if the actuator isn't working? Makes me think the circuit for that is stuck in the open position causing your battery drain. I would think your battery would drain when the car sits over night as well. That and the light are the only two items I can think of that could cause a drain.

 

Good old-fashioned key works just fine! I'd favour the actuator as the culprit if the problem happened all the time - but the drain only happens when the trunk is open for a prolonged period. Monday to Friday - the car starts and runs perfectly. Saturday afternoon after the trunk has been open for 40 minutes or so, the battery is flat. After a boost, no more problems until the next time the trunk is open. I have now disconnected the actuator while I await a replacement.... and I also discovered that the centre brake light is occasionally not working, so removed that and cleaned the connectors and it now seems fine, So maybe that has something to do with things. The real test will come when I next leave the trunk open.... stay tuned