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Hi All,

Was there a definitive resolution to this?

I have an 2011 Audi S5 Cabriolet with similar issues. Currently I have the same issue with the brake malfunction warning and the electronic brake light flashing even though it is fully working.

It all started with a weak battery warning whilst driving, the car literally went dead after 15 mins so we had to pull over. Went back to the car an hour later and it started up again!!.... A mechanic found that once the voltage regulator plug on the alternator was removed, things seemed to get better. The current situation is:
  1. Voltage Regulator is unplugged from the alternator, if it's plugged back in the battery will not charge and will eventually trigger the weak battery warning.
  2. The brake malfunction issue happened after my mechanic reconnected the voltage regulator plug to the alternator recently to see if there was any change, this was a month or so ago. It triggered the weak battery warning and then screwed up the braking system.
  3. Battery randomly discharges overnight, not fully but you lose a few bars daily, if you left the car a week / 10 days the battery would be fully dead. There have been some weird scenarios where the battery shows 60% and then 5 hours later it was showing 90% (not sure how!)
  4. On the odd occasion if the car is driven a short distance and turned off. When you start it again after a few mins, the battery starts discharging, when you rev the engine hard once, it starts charging the battery again.
I am completely lost with where to begin. Any suggestions / ideas / help / tips (besides selling the thing) would be awesome.

Thanks All! 😊
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