Looking for any helpful advice on what is causing the issue. I have exhausted my limited technical knowledge on this. Big Thanks.. Got that annoying fault, car alarm siren going off randomly all the time. Further investigation found car alarm horn H12 error. Did a bit of research and found out possible cause is the internal battery pack has gone faulty or maybe got a bit water damage. Searched for a useful guide on part and location. Thought l would add it here for others who might find it useful. Car is audi A4 B8.5 The alarm siren was then located and removed, until I eventually purchased a second hand OEM replacement part. Audi (dreamer stealers) wanted £172 just for the part!! This was then fitted and worked less than a day until the same issue started again. Alarm siren going off! So the only way to stop it was to disconnect the siren again. Just to add that may help diagnosis. The red led on drivers door top panel which indicates the car is alarmed. This stays on constant for 30 seconds before flashing every second when you lock the car. Also noticed the 2 led motion sensor detection lights stay on sometimes. These are the ones located in the roof front interior lights panel. These little pair of red leds stay on when unlocked and driving. Then go off eventually. I have tried to disable the internal alarm sensor by pressing the switch inside the drivers door. This eliminates red, showing you have disabled the alarm motion sensors inside the car. Lock it again and leave it but the alarm still goes off. Please help if you can, so l can try and fix this and more importantly have peaceful sleeps and happy neighbours again!