RS5 Alarm System Failure Linked to Auxiliary Battery

A similar issue occurred with my 2013 RS4 last year. Having some experience working on Audi electrical systems, I first noticed the alarm system acting up intermittently. The system diagnosis revealed error codes related to the battery signal, specifically pointing to voltage drops. The auxiliary battery was indeed the culprit, showing signs of aging after about 8 years of use. The car battery check confirmed significant degradation in capacity. My workshop performed a complete electrical system test and confirmed the auxiliary battery was no longer holding sufficient charge. The repair included: Full system diagnosis, Battery replacement, Alarm system recalibration, Final testing of all affected components Total cost came to 330 Euro, including parts and labor. The fix resolved all alarm-related issues completely. To better assist with your situation, could you share: Current battery age if known, Specific error codes showing up, Whether you notice any other electrical issues, If the main battery has been tested recently This information would help determine if your situation matches what I experienced and whether the same solution might apply.

My 2015 RS5 was last serviced at 193935 KM and the workshop ran a battery problem diagnosis along with the regular maintenance. They identified a failing auxiliary battery and suggested replacing it. My car alarm system issues match exactly with what you described, intermittent failures and stored error codes. The battery signal test also showed voltage drops similar to your case. Getting quotes from different shops now, but most range around 400 Euro for a complete fix including parts and labor. Looks like I will need both the battery replacement and alarm system recalibration to resolve the electrical issue completely. Based on your experience, would you recommend any specific system diagnosis steps before proceeding with the full repair?

Thanks for the additional details about your RS5. Since our situations are nearly identical, I can confidently say youre on the right track. When my RS4 had these issues, I made sure the workshop did a complete battery check on both the main and auxiliary battery systems before proceeding with repairs. The voltage drops and car alarm malfunctions you describe are classic symptoms of an aging auxiliary battery. The quoted price of 400 Euro is reasonable considering the full scope of work needed, quite close to what I paid for the same fix. Before authorizing repairs, I recommend requesting: A full printout of all stored error codes, Verification that the main battery is still good, Testing of the charging system, Confirmation that no other electrical components are affected After my repair was completed, the battery alarm system worked flawlessly again. The workshop should also clear all stored errors and confirm the alarm system functions properly after recalibration. One thing I learned: dont wait too long once these symptoms appear. A failing auxiliary battery can potentially affect other electrical systems if left unaddressed.

Thanks for the thorough information. The electrical issue symptoms in my RS5 definitely match your experience, and the car battery diagnosis confirms we had similar problems. The fact that your repair fully resolved the battery alarm issues is reassuring. I just scheduled the work for next week. Asked for all the testing steps you mentioned, full error code check, main battery verification, charging system test, and complete electrical component inspection. The workshop confirmed they will include the system diagnosis, replacement, recalibration and final testing in the 400 Euro quote. Good point about not delaying the repair. I noticed some other minor electrical glitches starting to appear, so fixing this auxiliary battery problem now makes sense before it affects more systems. Will update once the work is completed, but based on your successful outcome, I feel confident about proceeding with the full repair. Really appreciate you sharing your experience. Having someone confirm the same issue and resolution helps validate both the diagnosis and repair cost.