I have spent the past few months getting to the bottom of an intermittent alarm problem. The alarm would go off for no real reason, seconds after leaving it, hours after leaving it, rain, sun - anything. Nothing was consistent. The car was plugged into diagnostics and the fault appeared to be the rear boot lock. I promptly replaced that and the alarm kept sounding so replaced the handle (the rear badge unit) and still no help. I checked all wiring and made sure the earth points were ok. Nothing worked.
I spent hours on the internet finding possible reasons. My car had an RNS510 retro installed so it was possible (although unlikely as my car is a late 2007) the gateway was at fault. I spoke to Eddie-NL who had new gateways for sale and he was so sure it was not the gateway causing the problems he wouldn't sell me one as he said it would be a waste of my money. At wits end bought a new gateway............... Eddie was right it wasn't that!! Found a thread that mentioned the convenience module could be playing up, got a new one fitted, wasn't that either. I got to the point of having to lean into the car and lock the drivers door and boot on the button drivers side and park another car really close to the open passenger door each night as my neighbors were rightly somewhat upset with months of sleepless nights.
I had started to notice clicking sounds (like relays going off) when driving coming from the steering column and every now and then the doors would unlock themselves when driving. Eddie had a steering wheel for sale I wanted and I mentioned this to him when buying the wheel and he said he had come across the inner ignition switch failing. He was kind enough to sort a replacement out for me. Got it fitted (shear bolts are a b****r to drill out!!!) and coded. Its now been 3 weeks without the alarm going off for no reason. Thank you Eddie!!!
I could not find this when I was looking so I hope people with a similar issue can get some assistance from this and save themselves a huge bill and neighborly happiness.
