RS5 Alarm System Failure: Battery Issue Alert

I had a similar battery problem with my 2015 RS5, which shares many electrical components with the RS5. Based on my repair experience, this definitely sounds like an auxiliary battery failure. The system diagnosis revealed the alarm system was getting inconsistent battery signals. After checking the main and auxiliary batteries, it turned out the auxiliary battery was completely discharged due to age, a common issue around the 8-10 year mark. The workshop performed: Full electrical system testing, Car alarm system diagnosis, Auxiliary battery replacement, System reset and recoding Total cost was 330 Euro, which included parts and labor. The fix has been solid for over a year now with no recurring issues. Before suggesting more specific solutions, could you share: Current mileage, Any recent electrical work done, Whether the main battery has been replaced before, If there are any other electrical issues This information would help determine if your case matches what I experienced or if there might be other underlying issues.

Last serviced 2 months ago at 179838KM. The battery alarm issue started right after checking the engine codes at a workshop. The car alarm triggered out of nowhere a few times before failing completely. My main battery was replaced 2 years ago and tests show its still good. Interestingly, the parking sensors also started acting up around the same time the alarm system failed. Makes sense that the auxiliary battery could be the culprit since these symptoms match what you described. Will get both batteries tested to confirm before replacing anything.

Thanks for the additional details, which definitely align with my previous auxiliary battery diagnosis. When my RS5 had this electrical issue, the parking sensors also behaved erratically before the car alarm system failed completely. The timing of your problems starting after an engine code check is significant, in my case, the diagnostic procedure seemed to highlight the weakness in the aging auxiliary battery system. The battery signal became unstable, causing cascade failures in connected systems. Your mileage and battery age match the typical failure pattern I experienced. With the main battery testing good, and these specific symptoms (parking sensors, unusual alarm triggers), I'm even more convinced this matches my auxiliary battery problem. A quick tip from my repair experience: have the workshop check the auxiliary battery charging circuit while testing. In my case, they found minor corrosion on the connections that needed cleaning for optimal performance after the replacement. The repair bill should be similar to what I paid (around 330 Euro), assuming no additional electrical issues are found. Since you're having identical symptoms to what I experienced, replacing the auxiliary battery should resolve both the car alarm and parking sensor problems.

I appreciate everyone's detailed input. After comparing your experiences with my situation, I'm confident the auxiliary battery is the likely cause. The battery alarm symptoms match exactly, unusual triggers followed by complete failure, plus those erratic parking sensors. Really helpful to know about checking the charging circuit and connections too. My next step is scheduling the battery check at a workshop to confirm the auxiliary battery diagnosis. The 330 Euro estimate gives me a good baseline for the repair cost. Makes sense to address this now before it causes more electrical issues. Will update once I get the battery signal tested and hopefully fix this car alarm problem for good. Thanks again for helping me avoid unnecessary part replacements.