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 😃

 

 

Welcome.

 

It may be the Alarm Battery.

The Service book that came with your 2011 car showed the Siren alarm including it's battery as due replacement at the 5th fixed Service. 2016.

 

Many are still on the original and some are already replaced, and some got a battery and fitted that and never changed the whole unit.

 

There are threads on the forum about that. 

I would recommend fully charging your car battery on a long, low slow recharge - taking it out for a mile or two run wouldn't even replace the charge from starting the car for the run, then if you turn any other electric on you are further lessen the chance of the alternator getting anything back into the battery.

 

Your alarm battery could also be down but the low car battery also won't help and cause the alternator to have to work harder.  Recharge or replace your car battery and you might find your alarm improves and less likelihood of more electrical and computer program problems.

 

A battery is just a store, bit like a bank account you are making more withdraws than deposits and then ends in misery.

 

 

Do you want to retain/fix the alarm, or would you happy without it? Finding and removing the sounder will solve the problem if you're not bothered.

I think there's no chance it'll be anything to do with the car battery.

 

@Tog1966 if your car insurance is predicated on an alarm fitted to the vehicle you would need to tell them about its removal, if it's not or you don't care, no worries.

 

A low car battery can affect an alarm system, if it does properly fully charging the battery will help sort it unless there are other issues with the car alarm separately.  If charging or changing the car battery helps the alarm great, if it doesn't the car battery still needs recharging anyway - unless you decide to replace the battery with a new one which might be a good idea given your use.  New battery or old it might be an idea to use an appropriate battery charger or maintenance charger as new batteries can still go flat from lack of charging and limited vehicle use.

 

A battery that is in a low state of charge even if it starts the car and the lights seem bright enough can still be too low for the likes of the computers and their programs and they car throw up weird happenings, they might throw up warning(s) or might not and just mess you around.

 

https://www.startrescue.co.uk/breakdown-cover/motoring-advice/safety-and-security/why-does-my-car-alarm-keep-going-off#:~:text=Your alarm system needs a,the alarm could go off.&text=Find out about how to replace your car battery.

 

Edited 30 March, 20224 yr by nta16
spelling

Whatever you do dont mention the war................

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

10 hours ago, J.R. said:

Whatever you do dont mention the war................

 

Noted - ta, Sybil.

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.

21 minutes ago, Tog1966 said:

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.

You could test that hypothesis by unplugging the cable that goes to it and see if the same symptoms return. 

54 minutes ago, Pete_Ex-Wino said:

You could test that hypothesis by unplugging the cable that goes to it and see if the same symptoms return. 

 

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.

 

😩

 

 

I never worry about 'disabling' an alarm and the insurers and the car being stolen.  Hopefully not recovered.

 

If the thieves are caught are they going to grass me off because the alarm did not work?

 

Even if an alarm is working that does not stop anyone doing a smash and grab of stuff from the car.   

 

Double-check the door open microswitch functions by leaving the lights on, remove ignition key and open driver's door. See if you get a warning tone 'lights left on'?

 

6 minutes ago, Pete_Ex-Wino said:

Double-check the door open microswitch functions by leaving the lights on, remove ignition key and open driver's door. See if you get a warning tone 'lights left on'?

 

 

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.

1 hour ago, Tog1966 said:

Battery voltage now 12.1V, so the quicker I get that sorted the better really.

Regardless of your current alarm issues your car battery is very low.  Car batteries are one of the most oversold parts, often if recharged properly they can be fine but as I put before I think in some cases including yours you're best to buy a new good quality battery to save further hassle in the future.

 

I don't like alarms or immobilisers, I have neither on my car, other than the feeble ignition key steering lock but I know insurance requirements vary with policies so just mentioned about the disabling it in case Tog1996 hadn't thought or known about it, what people do with the information is up to them

 

Edited 31 March, 20224 yr by nta16
spelling

4 minutes ago, nta16 said:

Regardless or your current alarm issues your car battery is very low.  Car batteries are one of the most oversold parts, often if recharged properly they can be fine but as I put before I think in some cases including yours you're best to buy a new good quality battery to save further hassle in the future.

 

I don't like alarms or immobilisers, I have neither on my car, other than the feeble ignition key steering lock but I know insurance requirements vary with policies so just mentioned about the disabling it in case Tog1996 hadn't thought or known about it, what people do with the information is up to them

 

 

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!

Change your car battery, if the alarm issue goes it can be put down to coincidence.

 

Your alarm could possibly have other issues but you need to change your car battery anyway, I've know people go on months, and even a couple of years with old over-priced and over-valued cars called classics, with issues that where sorted by changing the car battery.

 

6 hours ago, Tog1966 said:

 

Excellent idea, just disconnected the cable and unfortunately, no alarm, so that blows my theory about the bonnet sensor.

 

 

 

 Don't just change the battery - get it tested by someone with the correct knowledge/equipment who can carry out all the correct tests rather than just looking at voltage - they may be able to perform an alternator test while the tester is clipped on the battery. Batteries do not have a use by date, and this is not a Tesla so a battery is not critical to the running of the car and may have no effect on the alarm with this minimal voltage drop on the battery.

 Regarding the bonnet switch, is this a normally open or normally closed contact when the bonnet is closed as unplugging may not give the expected result - Wino may provide the answer based on a wiring diagram.

http://briskoda.net/forums/topic/460585-alarm-keeps-going-off

 

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.

 

5 hours ago, Tog1966 said:

Quick update, I installed a new battery at lunchtime, alarm fuse back in and so far, so good 🤞

I'll start the chorus - "It's just a coincidence".  Will the others join in, cum on,  🤣

 

Don't celebrate too soon, you've been told it won't be the car battery by others and they might be right if the alarm or other car systems have other issues.

 

And bear in mind even though a battery is new it's still just a store that with heavy use and/or abuse can be depleted possibly getting you back to square one.

 

Be nice if you could report back in a month or three and say if the situation is the same - or it would bring great joy to some if you could report the alarm issue has returned and it's not the car battery.  Think of their little faces lighting up, how could you deny them a little joy.

 

5 hours ago, Tog1966 said:

I think given the old one was the original, it'd done rather well.

Yeap not a bad run at all.  With the older cars they'd last longer but those didn't have so much of the unnecessarily complicated (VW) computer programs ready for hidden cheats.

 

This battery won't last as long because the previous battery had its life with a new car with new parts and components, with this battery many of those parts and components are now 11+ years old so must have some wear on them.  If the previous battery was playing up for some time it'd be a good idea to test the charging system, that would have been working harder too to make up for the battery, to make sure it's n good state of health to help the new battery cope with its demands and not upset any of the car's other systems.

 

I've been charging my neighbour's very small car battery (obviously not a German car) for 26+ hours and the green light come on after it got dark and cold outside, oh well, it'll wait til tomorrow, as long as it's not raining otherwise Thursday, no panic rush charging in this household. 😁  He won't min, especially when he sees he got his car cleaned and polished during the wait.

 

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. 🙄

13 minutes ago, Tog1966 said:

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.

 

Have you got a dash-cam or something connected? If it's running constantly then that could be knocking hell out of your battery.

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.

49 minutes ago, Tog1966 said:

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.

Yep, keep an eye on it over the next few days, if there's a significant drain, you'll see the resting voltage gradually drop day by day. 

 

Do you plan to just leave the alarm fuse out? I don't think there will be any downside to that, but can guide you to alternatives if you need.

 

Not sure if mk2 is as easy, but on a mk1 it's remarkably easy to take the whole front door(s) off to improve access to the wiring loom. Just unplug the connector(s), undo one screw that holds the checkstay to the door, two nuts that hold the hinges together and lift off.  Only thing to be aware of is the weight of the door, so an assistant is advisable, especially when re-fitting door to avoid scratching paintwork. One person lifts/holds in approximate position, other one aligns both hinges from up close.