Help Please Audi car alarm siren keeps going off randomly

[A4A4]

Looking for any helpful advice on what is causing the issue. I have exhausted my limited technical knowledge on this. Big Thanks..



Got that annoying fault, car alarm siren going off randomly all the time.

Further investigation found car alarm horn H12 error. Did a bit of research and found out possible cause is the internal battery pack has gone faulty or maybe got a bit water damage.


Searched for a useful guide on part and location. Thought l would add it here for others who might find it useful.

Car is audi A4 B8.5

The alarm siren was then located and removed, until I eventually purchased a second hand OEM replacement part.

Audi (dreamer stealers) wanted £172 just for the part!!

This was then fitted and worked less than a day until the same issue started again. Alarm siren going off!

So the only way to stop it was to disconnect the siren again.

Just to add that may help diagnosis. The red led on drivers door top panel which indicates the car is alarmed. This stays on constant for 30 seconds before flashing every second when you lock the car. Also noticed the 2 led motion sensor detection lights stay on sometimes. These are the ones located in the roof front interior lights panel. These little pair of red leds stay on when unlocked and driving. Then go off eventually. I have tried to disable the internal alarm sensor by pressing the switch inside the drivers door. This eliminates red, showing you have disabled the alarm motion sensors inside the car. Lock it again and leave it but the alarm still goes off.

Please help if you can, so l can try and fix this and more importantly have peaceful sleeps and happy neighbours again!

 

[Stonefish]

I think if you press the button on the keyfob twice the deadlocks lock, but the alarm is off. If someone could confirm this??

 

[A4A4]

I think if you press the button on the keyfob twice the deadlocks lock, but the alarm is off. If someone could confirm this??

Thankyou @Stonefish

Tried it deadlocked but this still arms the car alarm, I should imagine. I don't think it turns the alarm off. It did not in my case, left it deadlocked and the alarm siren still went off on its own.

 

[rum4mo]

@A4A4, I'd agree with there, the most a double press should do is to disable any sensors for travelling on a boat or train.

I'd hope, but in a kind way, that your used next one is also faulty, but how to prove that - maybe find a friend that is willing to swop for a few weeks or days?

Edit:- what is the health and age of the car's own battery?

 

[A4A4]

@A4A4, I'd agree with there, the most a double press should do is to disable any sensors for travelling on a boat or train.

I'd hope, but in a kind way, that your used next one is also faulty, but how to prove that - maybe find a friend that is willing to swop for a few weeks or days?

Edit:- what is the health and age of the car's own battery?

Thanks for the help @rum4mo

I did think the second hand siren, has a chance to be a dodgy one. So have to think about what to do about that.

The car battery is a good question. The AGM car battery will be 6 years old from new in September, So it could be that. Last time I looked it was medium health around 50% charged. But I have fully charged it recently and left on a trickle charge for a couple of days. Fitted the siren but it still went off on its own eventually that day.


Just a thought out of this now, if the car battery was low. Why no warnings battery lights on the dash rather than warning you via sporadic alarms going off.

The AGM car battery change maybe, maybe the next move. Been quoted £160 fitted + £30 coding.

 

[Boundy]

Where are you? If close to be I could code your battery for free

 

[A4A4]

Where are you? If close to be I could code your battery for free

Not a problem but Thanks for the kind offer @Boundy but you would be a bit too far south.

 

[rum4mo]

Is there any chance of you opening up both these alarm assemblies, more the new one, to see if you can charge its internal batteries?

 

[A4A4]

Is there any chance of you opening up both these alarm assemblies, more the new one, to see if you can charge its internal batteries?

Tried opening the original one and failed miserably, could not get it open, tried going around the edges with a stanley knife, then tried to prise it open with a screwdriver. Would not budge...............In the end, threw it hard on concrete garage floor to smash it open. Still would not pop open. Frustration won in the end and it ended up internally broken. No surprise..

 

[Stonefish]

My sisters TT had a similar problem which was eventually tracked down to the alarm back up battery being corroded. Before I reached that conclusion I first disconnected the motion sensor in the over head console (with the reading lights etc). Waited to see if the alarm triggered. This didn't work so I disconnected the micro switch under the bonnet. Didn't fix it. Then I used VCDS to check stored codes in module 09 Central Electrics. On the TT measured value blocks MVB 20 to 23 show what triggered the last 4 alarms. Should be similar for A4. In the case of my sisters car the value "Alarm Source Trigger" was 22 which is the backup alarm battery. Not sure if you can get hold of someone with VCDS or whether OBDeleven or similar can do the same thing.

She did take her car to her local AUDI dealer who changed the motion sensor which didn't cure it. Luckily she managed to get a refund.

Sorry, my double button press advice didn't work. :-(

 

[rum4mo]

There are online guides to opening up these siren packs, I've never tried to do this, so far not had any need, but if you can't get your money back, I'd be opening up the second one carefully and making sure that its internal battery pack was getting fully charged, or remove its wiring and try charging both the batteries individually . Also try to find if the battery charging circuit's incoming supply is still there and not fused by the previous siren pack failure.

 

[RAF_S7]

Can you get someone to scan the car with VCDS?
You could have a faulty switch (doors/bonnet/tailgate) and end up chasing your tail and replacing perfectly good parts...

 

[rum4mo]

Can you get someone to scan the car with VCDS?
You could have a faulty switch (doors/bonnet/tailgate) and end up chasing your tail and replacing perfectly good parts...

The only thing wrong with that suggestion is that the opening post said that the fault had been confirmed as being this siren pack - but is it still the only fault being logged, a re-scan needed I think.

 

[A4A4]

This is the original X431 DIAG scan report

Came up with these faults

Which pointed me to look at the alarm horn for the issue.

Will VCDS show up something else?

 

[Willenium]

The fact that your LED stays lit for some time after locking before going into pulsing suggests the battery in the siren is low. My B6 did this until I replaced the unit and then all was well (flicker briefly on locking/arming and then pulse). I've not had one apart but I did read a guide before where someone made up a external powerpack for it with some rechargeable AA's. Saves having to spend out on new units each time although in fairness you might only ever do it once.

 

[A4A4]

Bit of a update.............Not fixed...

Bought 2 x replacement parts, but the alarm stills goes off randomly. So the siren works okay. It is much louder!

Cleared the codes 01134 Alarm siren. Re-scanned and all clear.

Only thing getting now (still) are these three things.

1 - The drivers door LED stays solid on for 30 seconds, then flashed normally every 2 seconds.
2 - The two internal alarm motion sensor LEDs are solid on. (located on the roof lining next to the interior lights panel)
3 - No beep sound, when alarm is armed (armed on or off)

Scanned again( using Carista) and no new codes, so at a loss on what might be causing it. Suspect the door latch or interior motion sensor. But not convinced since NO code errors flagging up for these.

Its due for it's MOT mid-September, hopefully the garage has got a better VCDS scanner, which will show up more Audi errors.

Fed up of chasing my tail on this.

So for now the working siren is disconnected from the loom.

 

[***DK***]

Does it still go off if you press the motion sensor kill switch on the edge of the driver's door before locking the car? Wondering whether that might help understand if it's motion sensor related or not.

Sent from my ONEPLUS A6013 using Tapatalk

 

[A4A4]

Does it still go off if you press the motion sensor kill switch on the edge of the driver's door before locking the car? Wondering whether that might help understand if it's motion sensor related or not.

Sent from my ONEPLUS A6013 using Tapatalk

The mystery fault find continues......

Tried and tested that today in my lunch break.......Removed the scuttle tray and reconnected the siren to the loom. Scanned and cleared errors for alarm siren.

....Pressed the (interior monitor/tow away protection) switch in the inner drivers door panel.

This LED illuminated red, so active.

Locked the car and played dead fish inside for 1 minute and then waved my arms to alert the interior motion sensors.

BEEP! BEEP! BEEP! BEEP! the alarm siren activated!!!


Does this mean the tow away sensor switch is faulty?

Going to look on Ebay for a cheap replacement. If not, does anyone know where the fuse is for this?

Can you just disconnect and override that door switch. Never used the tow away function anyway.

 

[***DK***]

Not really sure on those answers but it's probably quite easy to find a full replacement overhead dome unit with sensors in from ebay if your trying to eliminate faulty areas. May be a duff sensor unit up there somewhere.

Have you had the overhead unit down and checked all wiring?

Sent from my ONEPLUS A6013 using Tapatalk

 

[A4A4]

Not really sure on those answers but it's probably quite easy to find a full replacement overhead dome unit with sensors in from ebay if your trying to eliminate faulty areas. May be a duff sensor unit up there somewhere.

Have you had the overhead unit down and checked all wiring?

Sent from my ONEPLUS A6013 using Tapatalk

@***DK*** Thanks

No, overhead dome unit has never been touched,( in 6 years) so could be a faulty sensor which has just packed in. Guess it's another mystery hunt.

Just don't get why a scan would not pick errors up for this, if it was at fault.

 

[***DK***]

I'd open that up, one torx screw in the sunglasses flap and pulls down. Check all plugs are pushed in properly. That's really the extent of my help. Good luck and keep us posted.

Sent from my ONEPLUS A6013 using Tapatalk

 

[A4A4]

Checked the wiring in the front interior light roof panel and all looks good, nothing burnt out of lose. It's all very clean.

Which one is the motion sensors connected too? and can this just be unplugged.

Does anyone know which is the one to disconnect?

See this is what I am getting when the engine starts. You see the 2 x motion sensor leds are permanently solid on.

Only go off when you lock and turn off the engine.

 

[Stonefish]

8k0 951 177 is the movement sensor module.

 

[JohnS3]

As far as I know the 2 LEDs are for ambient lighting. They have no link to motion sensing.

 

[A4A4]

As far as I know the 2 LEDs are for ambient lighting. They have no link to motion sensing.

Not sure if these pin head red leds are ambient lights. (apologises if I'm wrong)

As I don't have any ambient lighting fitted in the car, don't even have any footwell lights or glove box light and certainly no leds' in the door panels etc.

Can anybody tell me why these LEDS light up and what does it mean?

 

[***DK***]

They are ambient lights. Shine down on the mmi/gear stick controls. Albeit quite weak. Nothing alarm related. They should come on when dark enough outside.

Sent from my ONEPLUS A6013 using Tapatalk

 

[A4A4]

Ok thanks, will eliminate those red led's as very, very poor ambient lights.

Since the alarm still went off, even when I pressed the tow away protection alarm switch button.

I might as well buy a replacement oem switch. As the one in mine may be faulty.

And get this fitted when it goes for its MOT in couple of weeks.

 

[***DK***]

Only other last thing I can think of is keyless entry sensors gone bad in door handles. I have no idea if bad sensors would set the alarm off but they almost always fail due to water getting in. Do you have keyless entry? If you do, they are again a cheap and easy one to replace. Plenty of videos of YouTube.

Sent from my ONEPLUS A6013 using Tapatalk

 

[A4A4]

Only other last thing I can think of is keyless entry sensors gone bad in door handles. I have no idea if bad sensors would set the alarm off but they almost always fail due to water getting in. Do you have keyless entry? If you do, they are again a cheap and easy one to replace. Plenty of videos of YouTube.

Sent from my ONEPLUS A6013 using Tapatalk

No keyless entry fitted to mine.

So still chasing my tail on this.

 

[A4A4]

Bump.. Bit of a update. 3rd time lucky maybe with a alarm siren?
Could not resist it when l saw a 2017 Audi A6 breaking, surely this alarm siren from that aged car should work. Bought for a decent price, so not a big hit on the wallet.

Fitted it 4 months ago but this time no sound, no beeps, still nothing. So just left it fitted and all connected. Still in today and deadly silent. Lol.

The problem obviously lays somewhere else. Suspect water in the cabling loom or simply needs a new car battery, which it's not quite ready for one yet. Blame lockdown!


This was the last and final try on this! Refuse to pay £167 for a new one. Only to fail again in a fews years. To be honest not really that bothered now, the car has no sounding alarm. No big deal, everyone ignores them anyway.

Good luck with anyone else gets this mystery and hope you have better luck in resolving.
Hope its just as simple as replacing it with a second hand alarm siren!

 

[***DK***]

I actually had this on my last b8 Avant and never managed to fix it. I tried a second hand siren and it still never beeped or sounded. Mine actually got nicked off my driveway, but like you say it wouldn't have stopped them even if it had sounded, it was gone in a matter of minutes.

Sent from my ONEPLUS A6013 using Tapatalk

 

[155limit]

I had same issue a4 2.5 cabby , when rained heavy usually a day later , alarm would start , i tried locking the car with key (but alarm would kick back in) ended up removing battery terminals (so did not send neighbours crazy),, I found water had been getting into the boot/truck , i used a heat gun (from distance to dry ) then contact cleaner on connector below , even when drying the fault is intermittent so the car thinks the boot has just been opened while locked so alarm is triggered , this happened 3 times in 2 years