2009 A6 parasitic battery drain - Audi Forum - Audi Forums for the A4, S4, TT, A3, A6 and more!

Aug 10, 2022 | 10:15 PM

TurkeyCreekDad

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2009 A6 parasitic battery drain

Hello all, I have strange issue that I cannot seem to get any good help on. This is a 2009 Audi A6 3.0T V-6 that is in really pretty good shape, minus one major problem.... it's always dead. After a day or two, the voltage on the battery will drop as low as 9V requiring a charge (after climbing into the trunk to pop the damn latch.)

This issue has been happening for over 6 months now and I have thrown everything, including the kitchen sink at it. Below is a laundry list of things that we have tried to resolve the issue. Any further suggestions would be very welcomed at this point.

New battery installed and configured
Tested each fuse with a multimeter for unusual voltage
Removed the battery from the keyfob during a series long tests, after reading that someone found theirs was randomly checking in overnight
Tested voltage with multimeter connected in series with the battery overnight
Discovered that the Navigation DVD receiver in the trunk always has a red LED indicator on even after it appears to have gone into deep sleep. Therefore, we have tested it for days without that fuse and the problem continues
Left it with our local Audi dealer for 3 months and they found zero issues that could be the culprit. They had a few hunches and some suggestions to fix it but nothing ever has.
The last thing the dealer tried was replacing the heater control unit. They said they had no scientific proof why that might help, but it 100% fixed two other Audi's of this generation, with this similar elusive problem.

I am about to run this car into the nearest lake if I cannot come up something that keeps it from dyeing ever couple days.

Thoughts?