ADVICE: Audi A4 battery drain trouble

[McSam]

Hi guys,

I've been having trouble with a rather serious battery drain on my '96 A4. This is the sort of thing that can take so much life out of the battery that the dashboard clock stops in less than a week, and the car is obviously totally dead. ECU reset, the works. It isn't the battery's fault, and it is something that seems to have got worse/started recently.

I pulled all the non-essential fuses I could, including the interior lights, stereo, boot light, central locking (two fuses for that yet it still works?), and the drain persisted. So I got an ammeter on the thing, testing various situations and found no more than a 10mA drain in any case I tested. Clearly that's not knackering my battery that quickly, but, it wasn't possible to test the current draw with the alarm fully armed, because it won't do it with the bonnet up.

The alarm makes a little beep when it's all locked, and I presume that's when it deadlocks everything. If I leave the bonnet open, I can lock the doors, but no beep and no drain.

So what do you think might be causing the drain? And what can I do to stop it? Thanks in advance!

[Fish981]

You'll need to know the current drain with everything locked. Run longer wires to the test meter under the car. Anything more than about 50ma is
wrong. Be aware the locking current drain may blow your meter up depending on which one your using.

[McSam]

I was hoping I wouldn't have to do that - it's going to be a pain since the bonnet has to be actually sealed shut to lock down! It's not even my ammeter so grafting croc clips onto it won't be too easy. I could do for absolute confirmation, but by deduction so far it looks like the drain is definitely present only when all locked. Question really is what could it be, and how to stop it?