996.1 Double Beep Issue - Help!

Hi Rennlisters, Long time lurker, first time poster here. I have a 2001 3.4 C2 that I'm in the process of restoring. It's unfortunately developed some rather loud and embarrassing alarm related issues and I would really appreciate some help. It all started when I recently had the dash apart so I could remove some unnecessary aftermarket hands-free kit that I discovered when fitting PCCM Plus last year. While I was plugging the head unit back in, the C3 fuse blew for reasons unknown. In hindsight, I should probably have disconnected the battery before doing this but it's all pretty simple plug and play stuff. The blown fuse caused a double beep, alarm siren chirp, several random alarm triggers, peed off neighbours and a minor dose of tinnitus. I changed the fuse and everything functioned normally again. I checked the alarm module fuse and that was also fine. Fast forward about two weeks and the car is double beeping again, but this time the C3 fuse is fine. There is now a really weird (to me at least) high pitch 'chime' from the front end when I try and lock or start the car. The alarm is triggering very regularly, regardless of what I do with the key and the central locking has become unpredictable. At one stage the car wouldn't start, with the interior lights dimming and illuminating on a loop in time with this front end chime. Now the engine does start, but occasionally and randomly causes the alarm to trigger on doing so. Does anyone have any clue what could be causing this? I'm afraid to do much further investigation for the sake of my neighbours (and my ears) but I'd like to fix it myself if possible. I've attached a video that depicts the suspect and unknown chime noise. In the video you can also hear the attempted locking, and subsequent unlocking. I'd say I thought it was a malfunctioning door latch somewhere, but it seems too suspicious that it has coincided with the electrical fault. The windows drop and raise as normal. Any advice will be gratefully received!

Probably the best course of action would be to have the car scanned and see if there are codes for anything the car sees as open (doors, front trunk/boot, etc) That being said I had a similar weak chime noise and it was solved with a combination of the above and also re-seating the connectors for the immobilizer box under the driver's seat. In this instance, the dealership had done some work on the car and not fully connected the connectors back up which caused the module to receive a partial signal. In the beginning, it would be periodic, then after driving a bit, the central locking wouldn't work at all. The scanning revealed the glovebox (not applicable to you) had a failed microswitch and the light was on all the time, it wasn't until scanning for codes, and sitting in the car in the pitch darkness, could I see the light and therefore what needed to be fixed.

Thanks for the reply! I suspect I may not have reseated the connectors perfectly when I checked the module's fuse. I did so with the passenger seat (RHD car) still in place, so it was a little bit of a stretch to gain access. That said, the car is currently locked and the alarm is not sounding, so I'm tempted not to touch it for now in case I make anything worse. I can get into my regular Indie next Thursday for a scan, I just hope they don't try and gouge me if the cause is actually something minor like the above. If the car thought something was just open, it would be a single beep, right? But then if a switch was malfunctioning, it would see this as a failure of the system and therefore a double beep? Before locking the car up I did notice that the frunk switch (electronic, not the early mechanical one) was non functioning, so I wonder whether that could be a contributor. It still works as expected when using the fob.

there is a ground wire involving the radio that is required to be connected or it will cause a double beep. i had the double beep and a PO installed after market radio. sure enough it was due to this ungrounded wire. however, I forget the actual details!!

*** Just a reminder - Disconnect the battery before doing any electrical/electronic based work It�s a minor inconvenience (having to reset radio code etc.) but can often save headaches Down the road (literally�). Good Luck!

With this many odd electrical issues I suspect that a Piwis or at least a Durametric will be needed to quickly get to the bottom of ALL the issues... But first, do a simple check to see if the rear floorboard/carpet behind the drivers seat is wet.....They can get wet without you even noticing and cause very strange and numberous alarm and convience function issues..

Cheers all for the suggestions. I bit the bullet and annoyed the neighbours one last time so I could try reseating the alarm module connectors. Sure enough, there was a tiny amount of play and this effort seems to have fixed the problem. Thanks Idaho911! It didn�t really occur to me that a bad connection could cause an intermittent/partial fault like that, I figured it would either be connected or not. You�ve saved me a couple of hundred pounds, I suspect!