VW Phaeton Alarm Fails Due to Auxiliary Battery Issues

Had the same battery problem with my 2011 VW Touareg. The auxiliary battery failure caused similar symptoms, car alarm malfunction and persistent battery signal warnings on the dashboard. The auxiliary battery typically powers the alarm system and other electronics when the main battery is disconnected. After diagnostic testing, it turned out the auxiliary battery had degraded due to age, which is common around 60-80k kilometers. The battery alarm and system warnings were accurate indicators. The repair involved replacing the auxiliary battery unit and recalibrating the alarm system modules. This was not a serious mechanical issue, but leaving it unfixed can drain the main battery and cause broader electrical problems. The auxiliary battery location makes replacement somewhat complex, requiring partial removal of interior trim panels for access. Worth noting that questionable previous work rarely causes auxiliary battery failure, its usually just age-related degradation. The symptoms match typical auxiliary battery problems. Would recommend having it properly diagnosed and replaced at a VW specialist who can properly code the new battery to the vehicle systems.

Thanks for sharing your experience with the Touareg auxiliary battery issue. The symptoms do sound identical to what I am experiencing. I had my Phaeton checked at a specialist and you were right, it was indeed the auxiliary battery that needed replacement. The car battery check confirmed the main battery was still good, but the system diagnosis revealed the auxiliary unit was failing. How much did you end up paying for the full repair on your Touareg? Also wondering if you have had any other electrical gremlins pop up since getting it fixed? The car alarm and battery warnings are my main concern right now, but want to make sure I am not missing other potential issues.

Just had the repair completed on my Touareg last week actually. The total came to 330€ for replacing the aged auxiliary battery, which resolved both the battery signal warnings and car battery alarm issues completely. Since the fix, all electrical systems are working perfectly again, no more battery problems or warning lights on the dash. The additional battery alarm system defective message has disappeared entirely. The repair shop did a thorough electrical system check during installation to ensure there were no underlying issues. The auxiliary battery replacement truly fixed everything in my case, no other electrical gremlins have surfaced since. The car alarm now works flawlessly, and all battery-related warnings have cleared from the system. Having a properly functioning auxiliary power system is crucial for keeping all the electronics running smoothly. Worth noting that once you fix this issue, regular battery checks are recommended to catch any future degradation early. But based on typical lifespans, you should be good for another 60-80k kilometers before facing similar battery problems again.

Went ahead and got the repair done at a certified VW shop last Thursday. The whole job ran me 380€, slightly more than your Touareg repair but still reasonable considering the Phaeton's complexity. The system diagnosis confirmed it was definitely the auxiliary battery causing all the electrical issues. The technician showed me how the old battery had degraded significantly. Really glad I got this fixed before it could cause more serious battery problems or electrical damage. The car alarm is working perfectly now and all those annoying battery warnings have disappeared from the dash. The mechanic also checked the main battery and other electrical systems while they had it apart, everything else tested fine. Massive relief to have this sorted. The car feels like new again with all systems functioning properly. Will definitely keep up with regular battery checks going forward to catch any issues early. Thanks again for pointing me in the right direction with the auxiliary battery replacement suggestion.