Advice please, my alarm is being triggered and flattens the battery

I suspect the fault codes you are getting are unrelated to the actual fault and are simply a consequence of the low voltage due to the fault.
To rule out the hazard relay you could disconnect it using the A2OC approved "make a fist" method when you are done using the car for the day. In the morning, if the battery hasn't gone flat you know the relay is the culprit. Additionally, there shouldn't be any fault codes. Diagnosis... villainous relay causing hazards to flatten battery and giving spurious fault codes and plenty of misdirection.

Unfortunately this is not a regularly recurring problem. Rather, it happens occasionally, quite at random. Other times, the battery appears to maintain a good charge. So, disconnecting the hazard relay overnight would tell me nothing.

It's a pain, not knowing whether or not the car will work when I go out to it. If I have to get to the back seat to access the manual tailgate release that is a real challenge and takes an absolute age. Swapping the batteries over is the easy part.

My A2 is an absolute lifeline for me, so I hope I get to the bottom of this before too long.
 
I'm not entirely sure where you're seeing that date, but it's quite possible I did one of the scans before resetting the clock in the car.
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The version of full VCDS makes no difference to the A2 as none of the updates contained files for the car. Think about it VCDS Lite is a much older version that never updates and works on the A2. Just look at the revision history on Ross Tech to see this.


I am curious if you do not lock / arm the car does the battery still go flat? Are you sure the boot light is off when closed? Is the car parked in the hot sun? Is there something setting off the interior monitor? ( have you tried disabling it? )

My thoughts are it is the alarm module that has expired. I know people have pushed the car battery to long lengths but the alarm module will be the same age as the car ( unless already changed for perhaps an even older one ) and the internal rechargeable battery ( NiCad ? ) has long since reached its maximum number of cycles and leaked as a consequence.
 
Unfortunately this is not a regularly recurring problem. Rather, it happens occasionally, quite at random. Other times, the battery appears to maintain a good charge. So, disconnecting the hazard relay overnight would tell me nothing.

It's a pain, not knowing whether or not the car will work when I go out to it. If I have to get to the back seat to access the manual tailgate release that is a real challenge and takes an absolute age. Swapping the batteries over is the easy part.

My A2 is an absolute lifeline for me, so I hope I get to the bottom of this before too long.
Understood. Mine was also random. I should take up Tom's offer if I were you and swap the relay over. Your symptoms are definitely the same as mine were. Sometimes the best option is to logically assess the problem, and then eliminate the easiest possible cause first, rather than agonize and over analyse.
I'm beginning to sound preachy here, and I don't mean to.
Best of luck, Steve.
 
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I am curious if you do not lock / arm the car does the battery still go flat? Are you sure the boot light is off when closed? Is the car parked in the hot sun? Is there something setting off the interior monitor? ( have you tried disabling it? )

My thoughts are it is the alarm module that has expired. I know people have pushed the car battery to long lengths but the alarm module will be the same age as the car ( unless already changed for perhaps an even older one ) and the internal rechargeable battery ( NiCad ? ) has long since reached its maximum number of cycles and leaked as a consequence.

The boot light definitely goes off when the tailgate is closed - it's one of the things I checked yesterday.

The car is reasonably shaded where I have it parked.

Most of the time, the battery does not go flat, it maintains a good charge (so I doubt there's any significant parasitic drain).

Because I don't know when this is going to happen, I wouldn't be able to tell whether leaving the car unlocked had any effect or not.

I'm not sure whether my current B pillar alarm button functions or not. I got a new one from AT and will get it switched over, so I can be confident that I'm disabling the internal sensor.

I'm quite happy to change the alarm module which is clearly past its best. That's the sort of job that I would need to get done professionally, and it makes me more inclined to wait until @timmus is back in Lancaster and can assess the car in person.
 
One other question does the service flap close tightly and does it depress the alarm button? I silicone a 3mm thick washer onto the flat on the inner side of the service flap to ensure more travel on the plunger of the alarm switch. The alarm switch can also be knocked out of its location and false trigger.
None of your fault codes imply the switch is the issue but something cheap and easy to do as a preventative measure. Bonus is when you release the service flap it pops a bit further out when open.
 
Unfortunately this is not a regularly recurring problem. Rather, it happens occasionally, quite at random. Other times, the battery appears to maintain a good charge. So, disconnecting the hazard relay overnight would tell me nothing.

It's a pain, not knowing whether or not the car will work when I go out to it. If I have to get to the back seat to access the manual tailgate release that is a real challenge and takes an absolute age. Swapping the batteries over is the easy part.

My A2 is an absolute lifeline for me, so I hope I get to the bottom of this before too long.

HI Steve, how are you stopping the hazard lights from flashing when they've been triggered? ... if it's with your key fob then it's likely to be the alarm unit (battery) in the back of the car but if it's by switching off at the hazard switch on the dash then it is probably the relay within the flasher unit that's failed or failing ... the symptoms for me were random hazards flashing ... these relays cost a couple of pounds to change if you're handy with a soldering iron or about £70 for a new unit from the dealers ... this was the issue with mine and has been working since the fix.
 
Hi Steve .... further to my last comment ... if it's the hazard relay (within the unit) then you can disable the circuit by pulling fuse number 34, this will allow your indicators to function as it has a separate relay and fuse within the same unit ... I did this when parked up at the airport for a fortnight just in case!

Edit: that should be fuse 7 for the hazards and fuse 34 for the indicators
 
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Hi Steve .... further to my last comment ... if it's the hazard relay (within the unit) then you can disable the circuit by pulling fuse number 34, this will allow your indicators to function as it has a separate relay and fuse within the same unit ... I did this when parked up at the airport for a fortnight just in case!
Morning Tom,

If you're above post is to disable the hazards alone then removing Fuse 34 will not achieve this, it will only disable the indicators/turn signals:

image (4).jpg


Maybe you meant removing Fuse 7 as the quick fix..

Hopefully Steph @steve_c now has a road to a solution with all the information provided so far.

Kind regards,

Tom
 
Morning Tom,

If you're above post is to disable the hazards alone then removing Fuse 34 will not achieve this, it will only disable the indicators/turn signals:

View attachment 99366

Maybe you meant removing Fuse 7 as the quick fix..

Hopefully Steph @steve_c now has a road to a solution with all the information provided so far.

Kind regards,

Tom
Hi Tom, you're right , it's fuse 7.... I will edit the above comment 👍👍
All the best ... Tom
 
Evening Steph,

Here are the parts that should deal with your current issue:

A39CD6CF-63B2-4973-B142-881E0BF98F98.jpeg


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They have been rescued from the garage and ready for fitting Sir.

These can be fitted reasonably quickly.

Only time will tell if it finally resolved your issue. That said with a replacement CCCU already included into the mix them there isn’t anything left to replace.

Kind regards,

Tom
 
HI All
I had a similar random alarm fault on my in laws 2003 polo 1.4 tdi. On a full check via vag com on the vehicle, i couldn't find anything wrong with it. All Doors showed locked unlocked or safe, boot lock same. My retired mother in law only uses her polo for shopping and family visits(no more than 50 miles per week) so i thought maybe low battery. So I took battery off and charged it up, took car out for an hour. After a week of no false alarms the car decided to alarm at 2 am in the morning. Very stress full for her. So again i scanned her car, again no issue found. So i manually disconnected the interior motion sensor, as for some strange reason the car wouldn't allow me to disable interior monitoring. Either via vagcom or via interior push button. It has been over 6 months now and no alarm. Could be worth a try??
Best of luck
 
Reading through the thread, other than fault codes, which may well be down to the battery going flat, there is no confirmation that the alarm is actually being triggered.
The no comms to alarm horn is indicative of a failed sounder, which is known to cause battery drain. The sounder, and other suspect, the hazard relay seem to be the right first move.
Mac.
 
I am No expert on cars but i try.
As said in my post on a full scan using vcds (full version) I couldn't find any probable cause for the alarm to be triggered on the polo, yet it went off all guns blazing sounder hazards etc.
As the polo and A2 probably share the same type of alarm i thought the information could be useful.
Best of luck
 
Reading through the thread, other than fault codes, which may well be down to the battery going flat, there is no confirmation that the alarm is actually being triggered.
The no comms to alarm horn is indicative of a failed sounder, which is known to cause battery drain. The sounder, and other suspect, the hazard relay seem to be the right first move.

The no comms to alarm horn only shows after the battery goes flat, so may well also be caused by that.

I've rescanned the car, and it now has no fault codes, other than the ones related to my 1st lambda sensor and the G263 evaporator sensor. Both issues I know about and am planning to deal with.
 
The no comms to alarm horn only shows after the battery goes flat, so may well also be caused by that.

I've rescanned the car, and it now has no fault codes, other than the ones related to my 1st lambda sensor and the G263 evaporator sensor. Both issues I know about and am planning to deal with.
Does the alarm horn comms code clear when you scan with a good battery?
Mac.
 
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