Ever since I've installed my subwoofer last week the alarm has been going off intermittently. I've ran various tests but it's a long winded process due to the delay between trying something and waiting for the alarm to go off (several hours) before moving on to the next idea. Im about to run out of possible physical causes so my latest theory is that disconnecting the starter battery for a day has depleted the battery backup in the alarm and that is causing the odd alarm behaviour. This is something I've experienced on a VAG car in the past, so perhaps this is the same problem. The other causes could be I've nicked a wire (unlikely but you never know) causing a partial short / earth or disturbed a connector. I was hoping someone could confirm the locations of the alarm siren - I'm pretty sure it's in the bulkhead scuttle, but there are two distinct noises on my car, one from the siren itself and another from elsewhere that beeps to confirm the alarm has gone off. And does the siren actually contain a battery backup? Also where is the Cobra control module? I've found a copy of a 2009 service manual that says its located near the left rear wheel arch, but having removed the access panel for the lights and had a grope around behind the carpet it all feels like solid metal back there. I wonder how much the loom has changed on mk3 ph2 compared to ph1? And lastly alarm fuse location(s) on ph2? None of this is helped by the fact it's an absolute pain to do any current draw tests on the car and access to most of the fuses is a nightmare!
OK confession time (and in case anyone searches for alarm issues) It appears the random alarm was caused by a tiny 2mm x 10mm flat piece of insulation I cut off when shortening the control cable for the subwoofer coming to rest on the trim directly above the tailgate lock striker. This must have been just about enough to prevent the boot lock latching fully but enough to be literally fractions of a mm away from activating the microswitch inside the lock. Infact so close, thermal expansion, a light breeze or even a cat breathing on it was enough to activate it! Glad I did one final sanity check before tearing the car to bits looking for random modules
