# How To Replace Batteries in the Alarm Siren



## John949 (Apr 12, 2017)

*Sourcing the Batteries*
The batteries are Varta 150mAh NiMH cells in two banks of three cells mounted vertically. The cells themselves are freely available in banks of three, but the particular vertical mounting pin arrangement seems to have been an Audi special and I haven't been able to locate a source. It's fairly easy to adapt a horizontal mounted pack though. Cheapest I could find was:

https://www.ebay.co.uk/itm/2X-VARTA-556 ... 2749.l2649

*Opening the Box*
The case halves are joined using a solvent glue, so you have to break it to get it apart. You could saw through the join all the way round but my advice is to make a cut a slot in the bottom corner big enough to get a decent sized screwdriver in and the lever it apart. The reason for this is that it will probably break and leave a small ridge which helps to re-align the halves when you come to glue it back together.

*Removing the Old Batteries*
I find that modern lead-free solder doesn't conduct the heat as well as leaded solder and so de-soldering things can be tricky, particularly large components on double sided boards. My advice is to cut the legs and deal which each pin one at a time. Two of the ground pins were particularly recalcitrant and I had to have the iron over 400 deg. I think there is a large ground plane which conducts the heat away very well, so take your time and don't risk pulling the tracks off the board. Once you have got the old pins out you need to clear the holes. The best way is to melt the solder and then use an air blast to blow the solder away. Failing that use a 1mm drill (carefully!) The batteries mount in the top right corner of the photo.









*Making up the Packs*
The original packs are on the left in the first picture, the green ones are the new.
Hopefully the pictures are pretty self explanatory, don't cut the original pins but fold them over the 'staples' as this holds them while you solder. Any copper wire will do so long as it is rigid enough to work with and obviously less than 1mm to fit in the holes. I used a single strand from some mains earth cable. Note that the + and - staples are slightly different widths in an attempt to 'Murphy-Proof' the assembly - obviously you need to get the polarities right.









































*Fitting /Re-Assembly*
Soldering is straightforward but do solder both side of the PCB, particularly if you drilled the holes out. I would recommend RTV to glue the two haves of the case, but YMMV.

*Testing / Re-Assembly*
I haven't included R & R instructions or testing instructions because I haven't actually removed my siren. This unit was donated by *Nidana* (we owe him a beer) so that a 'How To' could be written so maybe someone else could include the R & R instructions. How to diagnose a failed battery pack and test the siren would be good too.
If anyone wants to try this unit then you can have it if you PM me.


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## happychappy (Feb 9, 2015)

Excellent timing John, although I am wondering if after looking at your excellent detailed work my soldering skills are up to the task! 

After running a scan, discovering a PCV valve fault and correcting it I am left with a re-occurring fault that looks like it could well be the battery failing in the alarm Horn:-



















I would love to be candidate to test your repaired alarm horn and have pm'ed you


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## SwissJetPilot (Apr 27, 2014)

Outstanding work! I think this may be a another first for the Audi Mk2 Forum! Well done!!  

This particular *Varta* battery pack is often branded as "Mempac" and can also be found on Amazon as 3-cell Mempac 3.2V/150mAh. Be sure to check the voltage when you order as there's a 4-cell 4.8 volt pack which at first glance, looks very similar to the 3.2V. As shown in the DIY, these have a hard case, but they can sometimes be found with the green "shrink-wrap".

I just found this advertisement from a company called Cell Pack Solutions in the UK. From the marking, it looks like they've sourced the 8-pin OEM 2-pack and just relabeled it.

https://cellpacksolutions.co.uk/product ... 1-battery/

So far my alarm hasn't acted up, but as it's now 13-years old, I think I'll order a set of batteries and give this a go.


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## pcbbc (Sep 4, 2009)

Well done John.

Just a quick note on soldering batteries, which I am sure John only omitted because it should be blindingly (no joke intended) obvious....

Use as little heat as possible, for as short a time as possible.

If you're only soldering onto the folded over pins, as John has done here, you're probably going to be okay. But putting any significant heat into the pack itself is an obvious NO-NO!


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## happychappy (Feb 9, 2015)

Or boom boom....


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## SwissJetPilot (Apr 27, 2014)

I suspect when the internal batteries fail to take and hold their charge and the voltage drops below the expected 7.2 volts, the alarm siren (H12) registers a fault. Would be curious to look at the data blocks to see the expected values.

Obviously, if the batteries leak and wipe out the PCB (as they tend to) that's definitely going to cause problems. As these were never designed to last indefinitely, I think we can expect to see more and more alarm related problems reported in the Forum as our cars keep getting older.

Unfortunately the Audi wiring diagram isn't much help as with most devices with internal electronics, it doesn't go into that level of detail.


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## John949 (Apr 12, 2017)

Well done to SJP for finding someone with the right pack configuration in stock. I didn't think to search for something so specific as a special Audi part. Obviously the above part is a lot easier to solder but you still need to take care when removing the original. Slightly more expensive but probably worth it.


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## IPG3.6 (Sep 5, 2015)

excellent post! A cure for the dreaded random alarms going off!


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## SwissJetPilot (Apr 27, 2014)

@ *John949* - Yeah, lucky find actually. I found the 8-pin OEM batteries on Alibaba and Aliexpress, but they're currently not available.

By the way, what size pin-drill do you need to clear the through-holes in the PCB?


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## Steve in Ireland (Oct 13, 2017)

SwissJetPilot said:


> I suspect when the internal batteries fail to take and hold their charge and the voltage drops below the expected 7.2 volts, the alarm siren (H12) registers a fault. Would be curious to look at the data blocks to see the expected values.


I've been playing around with the "Deep OBD" app I posted about some time ago.
https://github.com/uholeschak/ediabaslib/blob/master/docs/Deep_OBD_for_BMW_and_VAG.md

My alarm did go bad about a year ago, and I replaced it with a newer, second-hand one. I used the Deep OBD the other day to retrieve (and clear) the stored error codes, and there was nothing relating to the alarm.

(The two codes it showed were a lean running error, which has not come back; and mid-range speaker, passenger side, open-circuit, which I knew about anyway, because it's not making any noise!)


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## SwissJetPilot (Apr 27, 2014)

@ *Steve in Ireland* - Interesting. Okay, here's a couple of questions 

1.) Other than being able to work on both VAG and BMW, what makes this App different than what's possible with a VCDS or OBDeleven?

2.) If you didn't have a fault code for the Alarm (typically 01134 - Alarm Horn (H12): No Signal/Communication), what prompted you to replace it?

You mean this one?


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## Steve in Ireland (Oct 13, 2017)

SwissJetPilot said:


> @ Steve in Ireland - Interesting. Okay, here's a couple of questions
> 
> 1.) Other than being able to work on both VAG and BMW, what makes this App different than what's possible with a VCDS or OBDeleven?


From what I've seen of VCDS screenshots, that product is both more professional and easier to use and understand. The only reason I began to mess around with Deep OBD is that it's free and unlimited, and seems to be able to communicate with every module in the car. I have been too nervous to attempt to change anything, because there seems to be no way to "go back" if you mess up. I have thought of enabling the arm/disarm chirp as a test.

A small catch is the the ODB dongle needs to be flashed with custom firmware in order to talk VAG protocols. The author gives instructions on how to do that if you have a standard dongle and PIC programmer. If you don't, you can buy a ready-flashed one from him. I assume he makes a small profit, which seemed fair enough to me.



SwissJetPilot said:


> 2.) If you didn't have a fault code for the Alarm (typically 01134 - Alarm Horn (H12): No Signal/Communication), what prompted you to replace it?


The symptom was the random sounding of the alarm, and internet search suggested that failure of the backup batteries was a common cause. Given that the faulty alarm still "works" in the sense that it can trigger and make a loud sound, perhaps the issue of "No Signal" does not arise?

I bought the replacement from the corpse of a 3-year-old Seat. It was £20.


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## SwissJetPilot (Apr 27, 2014)

Steve in Ireland said:


> ...there seems to be no way to "go back" if you mess up.


You're correct that both VCDS and OBDeleven (I have both by the way) do not have an "undo" option once you change the long code. But to be fair, if you run an Auto Scan BEFORE you change anything, it's pretty straight forward to change it back.

From the various comments on both VCDS and OBDeleven users, the problems arise when people don't read up on how to use them ahead of time and just randomly start ticking and unticking boxes and change the codes. Then when things suddenly don't work properly, they don't have a baseline to go back to.

This is why I encourage anyone who uses either the VCDS or OBDeleven (or similar device) to always run a baseline scan first and save and/or print it so you always know how your car was set at the factory. An Auto Scan will interrogate every available Address and report the OEM factory code for that Address. Then you can make all the changes you want and if it doesn't work out, you know what to set it back to.

This is from the very first Auto Scan I did when I first tried out my VCDS. This gives me all the factory codes for every Address so no matter what Byte or Bit I change, I can always go back.


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## John949 (Apr 12, 2017)

The PCB holes are 1mm. I suspect they are 'through hole plated' (i.e. there is continuity from top layer PCB to bottom layer PCB. If you drill them you risk breaking this but if you solder top and bottom you should be OK.

I did do a quick test on the old batteries. They took a fast charge fine (I have some specialist chargers from my model aircraft days) and sat at 1.4V per cell after charging (which is about what you'd expect) but quickly dropped to around 1.2V after about 12 hours under no load. Sometimes you can revive NiMHs by being a little rough with them (fast charging and fast discharging for a few cycles) but for this application I'd just replace them.


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## SwissJetPilot (Apr 27, 2014)

These particular Varta NiMH batteries are only good for "_5-years or 1,000 IEC cycles_". Given the last Mk2 was produced in 2014, even the the newest batteries (if they were factory fresh when installed in the siren) would be past that now.

View attachment Varta NiMH Button Cell 55615306060.pdf

@ *John949* - Looking back at the pictures from *Nidana* of the PCB before the battery packs were completely removed, do you think it might be better to leave the leads soldered to the PCB and just cut them away where they're welded to the battery pack?

This approach would avoid having to de-solder the leads from the board (less heat), eliminate the need to drill out the leads (no damage to the thru-holes) and require less heat in the repair soldering leads-to-leads.


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## happychappy (Feb 9, 2015)

Hi John

Been trying to send you a pm with no success, there are five in my outbox?

Have you received a thank you pm from me?


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## John949 (Apr 12, 2017)

Happychappy - yes thanks I got all 5! It's boxed up and addressed but waiting for me to get to the post office!

SJP - Possibly but might be a bit fiddly to get everything aligned nicely. There is always more than one way to skin a cat and the skill is in picking the easiest way that works. If I did it again I would still remove the old pins. There aren't any really heat sensitive components near the batteries so I might try my hot air de-solderer next time.


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## SwissJetPilot (Apr 27, 2014)

@ *John949* - I was also thinking for the average user, while they would have a soldering iron, they are less likely to have any special soldering/de-soldering tools. I'll admit I don't even have a 1mm drill bit, let a lone a hot air de-soldering device! 

@ *happychappy* - Would you be so kind and run a fault scan before and after you disconnect the siren. I'm curious if a fault appears if the unit is disconnected and what fault shows up. The only fault code I'm aware of for the alarm siren is:

_01134 - Alarm Horn (H12): No Signal/Communication_.

That may be the only fault code VAG has assigned H12 whether it's unplugged or if the NiMH battery has failed. Thanks!

.


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## happychappy (Feb 9, 2015)

John949 said:


> Happychappy - yes thanks I got all 5! It's boxed up and addressed but waiting for me to get to the post office!
> 
> SJP - Possibly but might be a bit fiddly to get everything aligned nicely. There is always more than one way to skin a cat and the skill is in picking the easiest way that works. If I did it again I would still remove the old pins. There aren't any really heat sensitive components near the batteries so I might try my hot air de-solderer next time.


Just looked and saw them all gone.... :?  look on the bright side, the swear box is full again....


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## SwissJetPilot (Apr 27, 2014)

:lol: No worries! I'm going to order some batteries myself and can check on mine when I do the replacement.


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## happychappy (Feb 9, 2015)

SwissJetPilot said:


> @ *happychappy* - Would you be so kind and run a fault scan before and after you disconnect the siren. I'm curious if a fault appears if the unit is disconnected and what fault shows up. The only fault code I'm aware of for the alarm siren is:
> 
> _01134 - Alarm Horn (H12): No Signal/Communication_.
> 
> ...


I will try and time it with my code reader pal as I don't have a code reader...still...


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## happychappy (Feb 9, 2015)

Update

Received the alarm this morning, thanks so much John.

Mate not going to be over till end of next week and after physically testing the alarm I am getting flashing lights but no sound, so am going in!

For the record a replacement alarm - 1KO 951 605 C is £163.51 inc VAT

After swapping out the alarm I am still getting no sound.

I understand that the 01134 code is a faulty alarm, so that would explain no sound, but whats the likelihood of the replacement alarm being faulty?










Would the 16346 code for the immobiliser have any bearing?










Could that be the cause of the no sound fault?

Any help would be much appreciated.


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## Nidana (Jun 9, 2018)

I have the immobiliser fault code and all I have read tells me a check sum is incorrect from some point. I'm guessing it was from last owner that lost a key and had another coded and then found the lost key. 
My alarm fault code was also the same and my alarm would chirp but not sound. So I fitted another alarm second hand and no I have chirp and alarm sounding.

Sent from my iPhone using Tapatalk


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## happychappy (Feb 9, 2015)

I'm hoping it's the alarm horn that's still faulty, I can blame you as it's your repaired alarm I swapped my one out for!   

I have been playing with my audio equipment recently and have missed the warning "rear spoiler alert" on a couple of occasions resulting in a dead battery, I am hoping it's this that has killed off my 11 year old original horn.

I believe your theory about the keys may well be a problem we share as my D.I.S shows three keys and I only have two.


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## Nidana (Jun 9, 2018)

I believed alarm fault was down to the batteries not that I tested them as it would chirp. 
Only really noticed alarm didn't sound when doing the headunit the car locked itself whilst I was still inside then I triggered the alarm but had no sound. This sent me into getting Carista at first as it worked on iOS but was very limited with what it could do compared to OBDeleven. Since OBDeleven has iOS now I have upgraded. 
It's a shame the alarm has a fault still possibly would have been nice for it to help someone out.

Sent from my iPhone using Tapatalk


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## happychappy (Feb 9, 2015)

John has suggested to check the alarm out by powering up with a 12v supply which I will do tomorrow, if this doesn't work I will return the unit, as requested, for him to fault find.

How do you find OBDeleven with iOS? Did you go for the Pro version?


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## Nidana (Jun 9, 2018)

It almost has all features now and I'm still learning with it. I've only coded the rear wing so far before they did a one tap feature for it. All my other coding was done before it was released by someone else. 
I ditched having a pc or laptop a long time ago as iPad pretty much did what I needed so didn't want to have to buy a laptop just to connect to a car once in a while so glad OBDeleven did iOS support. I do have pro version which is probably wasted at the moment but compared to Carista now it's leaps better. 
I leave Carista in the glovebox incase of breakdown now only. The main thing I wanted to be able to do though was check chain stretch. 
I will scan and save then look in the how to's at vcds guides to check the path to what I'm looking for disconnected from car and if I need it to be live data once I'm happy with the path reconnect and be nosey.

I'm sorry my donated alarm didn't give you better results fingers crossed it will soon.

Sent from my iPhone using Tapatalk


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## SwissJetPilot (Apr 27, 2014)

@ *happychappy* - If those scans were by someone who did it for you and they didn't clear the faults, it may be why the repaired alarm isn't working. Not saying it is, but it could be a factor. Run another scan, clear all the DTCs, run another scan to be sure all the DTCs are actually gone and try the alarm again.

Based on this menu from VCDS, it looks like there's an Adaptation possible. This could just be a way to change how the alarm works. I'm not sure to be honest, but it's worth looking into if you can.


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## happychappy (Feb 9, 2015)

Thanks Swiss, I am pretty sure he cleared the faults after I replaced the PCV valve.

He scanned the system, cleared the faults, I went for a drive and then rescanned and was left with the faults (and a few expected audio ones due to change of amp and head unit) noted above.

I am wondering if the can bus system has anything to do with the alarm as my audio T32 connector in the boot is currently only connected to the front speaker being driven by an after market amp?

Update

I replaced the Alarm Siren with an identical code matched (1KO 951 605 C) one from a 2014 Audi A5 and all is now fine.

Code reading friend can't come over this week but is hoping to drop by next week, I will get him to see what codes there are left.


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