RS4 Alarm System Failure Linked to Auxiliary Battery

I had a similar battery problem with my 2006 A4. Having some experience working on Audis, I initially tried basic troubleshooting when my car alarm started acting erratically. The system diagnosis revealed a failing auxiliary battery, which triggered multiple error codes. The battery alarm was the first sign something was wrong, followed by complete system failure. My workshop confirmed the auxiliary battery had degraded due to age, a common issue in these models after 15+ years. The replacement process took about 2 hours since they needed to access components behind the trunk panels. Total cost was 330 Euro including parts and labor. The technicians also checked the main battery and charging system during the repair to ensure there weren't any underlying issues affecting the auxiliary unit. Everything else tested fine. What year is your RS4? This would help determine if the repair process would be similar. Also, are you getting any specific error codes? The diagnostic information could point to whether your symptoms match what I experienced.

Year: 2004. Latest service was 2 months ago at 48435 KM. The battery alarm symptoms match my experience exactly. My car alarm stopped responding completely before I noticed additional electrical gremlins. After a thorough battery check, the workshop found a faulty auxiliary battery as the root cause. The system diagnosis also pointed to a failing main battery connection, which was causing inconsistent power delivery to the alarm system. Getting both issues fixed resolved all problems. The repair cost me 450 Euro in total. Make sure they conduct a full electrical system test while replacing the auxiliary battery to catch any related issues. My alarm system has worked flawlessly since the repair.

Thanks for sharing your experience. The combined battery issues you encountered really mirror what happened with my A4. When the workshop handled my auxiliary battery replacement, they also detected some corrosion at the main battery signal connections causing similar voltage irregularities. The alarm system problems are definitely a clear warning sign of battery troubles in these models. Getting both the auxiliary and main battery connections checked was key in my case too. Since your car has relatively low mileage, addressing these battery problems early likely prevented more expensive electrical issues down the road. My total repair costs were a bit lower at 330 Euro versus your 450 Euro, but the additional work on the main battery connections explains the difference. The complete system diagnosis proved essential for identifying all the underlying car battery problems. Has the alarm system remained stable since your repair? On my A4, the fix has held up perfectly for over 2 years now without any battery alarm warnings or electrical quirks returning.

I appreciate the detailed follow-up on the battery and alarm system issues. Yes, everything has remained completely stable since the repair two months ago. The alarm system works perfectly now and all the electrical gremlins have disappeared. The thorough system diagnosis was definitely worth the extra cost. While 450 Euro seemed high initially, addressing both the auxiliary battery and main battery connection problems prevented what could have been more serious electrical issues later. My RS4 is a 2004 V8 model with the original alarm system. For others dealing with similar battery alarm problems, I recommend getting a complete electrical test done rather than just replacing the auxiliary battery. The technicians spotted that failing main battery connection during their diagnosis, which could have caused more expensive issues if left unchecked. The workshop also mentioned these auxiliary battery failures are quite common in aging models, especially when approaching the 50000 KM mark. Regular system diagnosis can help catch these issues before they lead to complete alarm system failure.