Audi A3 Alarm System Failure: Common Siren Problems

I faced a very similar signal problem with my 2004 Audi A4, and I have some experience working on basic car electronics. The symptoms match exactly what I encountered, complete alarm system failure with fault detection codes showing. In my case, the alarm disarm function also stopped responding, which made accessing the car quite challenging. After some initial troubleshooting, my workshop found the root cause was a damaged wiring connection near the siren unit. Water had seeped in over time and corroded the plug contacts. The repair involved replacing the damaged cable section and installing a new weatherproof connector. The total repair cost was 95 Euro, which covered both parts and labor. Since then, the vehicle security system has worked flawlessly. To better assist with your specific case, could you share: Which fault code is showing? Have you noticed any water damage or corrosion around the hood area? Does your key fob still work for locking/unlocking? Are there any other electrical issues present? This would help determine if you are dealing with the same connection issue I had or if its potentially another component causing the security breach.

Last serviced 2000km ago and all was working fine. The fault code showing is 01134. My key fob still works normally for locking and unlocking the doors, but the alarm reset function doesnt work anymore. No visible water damage around the hood area that I can spot. The signal problem started out of nowhere while parked. When checking the alarm controller connections, everything appears properly connected, though I notice a slight clicking sound when attempting to arm the system. Would testing the siren with a multimeter help identify if thats the failing component?

Thanks for providing those details. When my A4 had this issue, I also heard that clicking sound from the alarm controller, it typically indicates the system is trying to communicate with the siren but failing to complete the handshake. Testing with a multimeter is definitely a good next step. In my case, even though the connections looked fine visually, the voltage readings at the siren connector were inconsistent. You should see around 12V when measuring between the power and ground pins. Since your key fob works for basic functions but not alarm reset, and given fault code 01134, this strongly suggests a siren communication fault rather than a complete automotive alarm system failure. The vehicle security system is likely functioning partially, just not communicating properly with the siren component. Before replacing parts, try this: Clean all connections at the siren unit, Check fuse box for any blown fuses related to the alarm system, Test voltage at both the siren and alarm controller connections, Listen for siren activation when having someone trigger the hood switch If voltage readings are normal but the signal problem persists, you might be dealing with an internal siren failure like I had, rather than just corroded connections. The replacement siren unit cost me around 65 Euro plus installation. Would you mind checking those voltage readings and sharing what you find? That would help confirm if we are dealing with the same issue.

Thanks for the input. After testing with the multimeter as suggested, I found inconsistent voltage readings at the siren connector, ranging between 8V and 11V instead of the expected 12V. This definitely confirms a problematic connection in my automotive alarm setup. I cleaned all the connections but the alarm reset function is still not working. Given the similar symptoms to your case and the unstable voltage readings, I will proceed with replacing the siren unit. The clicking sound from the alarm controller really seems to be the telltale sign of a communication failure between components. Will update once I have the new siren installed and confirm if this resolves my vehicle security system issues. The diagnostic steps you provided helped narrow down the problem and saved me from blindly replacing parts. Really appreciate all the troubleshooting guidance on resolving this alarm system fault.