Tog1966

Yes I'm happy to leave the fuse out whilst I'm diagnosing the issue. It's good to know the alarm won't be going off and annoying the neighbourhood, especially at night.

No nothing like that, I wonder that if by trying to diagnose, fix and test the problem by constantly locking and unlocking the car plus starting it up a few times, whilst not actually having driven it anywhere to allow a recharge, I'm actually causing something of a drain myself! I'll give it a good run out tomorrow and check the state of the battery as soon as I'm back, then monitor it over the next 24-48 hours to see if it's draining. I'm still suspicious of the door wiring loom, I've had a fair few of those wires break and have tried to reconnect them best I can but it's so tight in that space to be able to do the job properly.

Yep, just awoken from a nice afternoon nap by the alarm going off again, fuse removed to keep the neighbours happy, back to square one. Haven't driven the car since the battery was replaced, it read 12.74V out of the box yesterday, now showing around 12.45V having been in the car for just over 24 hours. Not sure whether that's to be expected, or I have a battery drain maybe. Ah well. 🙄

Quick update, I installed a new battery at lunchtime, alarm fuse back in and so far, so good 🤞 I think given the old one was the original, it'd done rather well.

Thanks Nigel, I appreciate your comments and pointing out the insurance thing, personally for me the administrator said it made no difference, but I guess there are some companies, policies and vehicles where it will be a requirement. The battery is definitely 2011, the negative terminal has 33 and 11 stamped on it, which is 33rd week of 2011 for Varta - I'm amazed it's lasted so long to be honest!

Yes the warning tone sounds, so the door switch is OK - I've kind of discounted the doors and boot though, because I opened and shut each one in turn and waited for the interior courtesy light to go out, which it did for all 5 doors after approx 22 seconds.

Excellent idea, just disconnected the cable and unfortunately, no alarm, so that blows my theory about the bonnet sensor. More annoying is the fact that the alarm just went off again, this time beyond way beyond the 30 second activation time, so back to square one, fuse 54 removed. Battery voltage now 12.1V, so the quicker I get that sorted the better really. 😩

Well fingers crossed, the problem seems to be resolved. I gave the bonnet sensor a good clean and blast with WD40 and since then, it's not gone off at all, so that may well have been the problem. I'd disabled the alarm by pulling fuse 54 so that it didn't keep going off overnight (I called my insurance company too who said that disabling the alarm didn't affect my policy at all), so that may be the end of it. I will however be replacing the 11 year old battery and getting a charger to keep it topped up, so thanks to all who contributed to the resolution.

Thanks to everyone who has replied so far, very much appreciated.

Hi everyone, I have a lovely shiny red 2011 Fabia MonteCarlo (HTP) with 67,000 miles on the clock and I've started having some issues with the alarm so I thought I'd share what I've found so far and see if anyone has any ideas or suggestions. Whenever the car is locked with either the remote or door lock, the alarm goes off after 30 seconds, every time. It's not a random thing, just every time the car is locked and the once the alarm system is activated, it triggers. I don't believe it's linked to the doors or boot, when each is shut the courtesy light goes off after about 22 seconds, so I don't think the alarm system thinks they are still open at all. I can't determine at this stage whether it might be the bonnet causing the issue. I next turned my attention to the battery, suspecting a voltage drop might be causing the problem. When the car is running I get a consistent reading of between 14.2V and 14.3V which I believe is spot on. When I switch the car off, the voltage drops immediately to 12.6V, but then over a matter of minutes has dropped to around 12.25V, which probably means it's only about 50% charged? Would this voltage drop be enough to fool the alarm system into believing there's a problem? I never have any trouble starting the car at that voltage. I have looked at the battery and the date code, and from what I can see, it may well be the original Varta battery supplied for VW AG, the date code starts C8C107 which from what I've seen is July 2011 - I've only had the car since July 2019 and there's no evidence in the paperwork that there has ever been a new battery and I've not had one under my ownership, so it's lasted pretty well if that's the case. The car isn't very often used I have to say, I literally take it out for a mile or two every week to give it a quick run unless there's a need for a longer journey to be made, whether that's the cause of the reduced voltage I don't know. The only other thing to mention, which is probably not linked in any way, is that I've had the usual broken wiring issues in the door harness so have done some wiring re-connection in the past. Looking forward to any ideas, I'm happy to replace the aging battery if people think that is probably the cause. Many thanks, Tog 😃