Alarm Triggering Mk 7.5

[sicario]

My alarm is randomly going off.

Started one day, kept happening over the course of a few hours, then stopped after a quick drive to check my battery at a local garage. Chalked it up to a one off, but then it happened again the following night multiple times.

Read a lot about door and hatch latches, lights, internal monitoring, and no amount of messing around helped. Can’t seem to work out a pattern to it either. Perhaps coincidence, but I had to have my heated screen replaced 10 days prior after a chip, so I thought something with the wiring on that, or perhaps a leak bridging a connection somewhere might have caused it.

VW think it’s the alarm siren battery through their fault finder, £500 to replace the unit. Cars approaching 4 years old, I’ve owned it for 1.5.

My question is, is it a common issue on Golfs? I would have expected the battery to last longer than 4 years if it’s a sealed unit!

Is their fault finder reliable enough, or is it just an indication?

Probably over thinking it, but the way my luck is going at the moment I’ll pay to replace it and it’ll keep happening. Do dealers usually charge for additional work if you pay for work that doesn’t resolve the issue?

 

[KyACRASH]

4 years is very long for the battery, I'd start there.

 

[sicario]

The car battery? That was my first thought as well, the garage I initially went to said it was 68% and fine on voltage.

The day it was the worst the car hadn’t been driven in 48 hours. But the following evening I did my usual commute 35 miles each way.

 

[sicario]

Picked up an obd scanner and it was reading 12 flat off and 14.9 on. Visual indicator on the battery is also yellow.

After you mentioned it, I do remember the infotainment system being unusually off the other day, so it definitely lost power.

Bit stumped why a garage okayed it when I specifically asked about the battery, and why the dealer thought it was the siren instead!

Going to replace the battery and hope it solves it. Its an Exide EFB and I know the previous owner didn’t use it much as it had only done 10k in 2 years. Going AGM this time.

Thanks for your help!

 

[Strange Mud]

12 flat is low

 

[kevinkar]

Picked up an obd scanner and it was reading 12 flat off and 14.9 on. Visual indicator on the battery is also yellow.

Yeah, I just had to replace mine over Christmas and it too was 14.9 on (alternator was working!) and actually less than 12 off. Though my Battery Tender and Noco Genius charger both showed the battery as fully charged, as soon as I removed them the battery dropped to less than 11 and was clearly gone. The indicator was also still yellow. POS indicator.

Freaking digital dash needs a voltmeter or something to show when the battery is low or not holding a charge.

I got an Optima Yellow Top for a replacement. Make sure to use OBD11 to reset the battery type so it charges properly.

 

[Strange Mud]

most times the indicator is a fluid sensor not indicative of overall battery health

 

[shovelhd]

I got an Optima Yellow Top for a replacement. Make sure to use OBD11 to reset the battery type so it charges properly.

What type did you code it to?

 

[kevinkar]

I believe it was:

Gateway
Battery adaptation:
Rated battery capacity: Changed to the ah the battery is rated for
Battery manufacturer: I entered in Optima
Battery serial number: I think you just need to change this by one number but I used the date like 2021121710 (date, time of day)
Battery technology: Fleece for AGM types (it's made up of some sort of glass mats empregnated with goo so "fleece" is the right choice.)

I think that was all I needed to do. So far so good.

 

[shovelhd]

I believe it was:

Gateway
Battery adaptation:
Rated battery capacity: Changed to the ah the battery is rated for
Battery manufacturer: I entered in Optima
Battery serial number: I think you just need to change this by one number but I used the date like 2021121710 (date, time of day)
Battery technology: Fleece for AGM types (it's made up of some sort of glass mats empregnated with goo so "fleece" is the right choice.)

I think that was all I needed to do. So far so good.

Thanks. I have VCDS but the adaptation should be the same. My original OEM battery is 4 years old now so I'm watching it. When it starts to go, I'll replace it with a Yellow Top, so this helps. Please post in here if you change these settings down the road.

 

[sicario]

And it’s back. 5 blissful days with no alarm then it’s going off with a vengeance again just in time for the weekend.

This time I found the fault code indicating siren voltage low. Brilliant.

Does anyone know if there’s a fuse I can pull to stop it going off? The unit itself looks unpluggable based off of google images, but I can’t find any information about removing it on a 7.5.

 

[KyACRASH]

And it’s back. 5 blissful days with no alarm then it’s going off with a vengeance again just in time for the weekend.

This time I found the fault code indicating siren voltage low. Brilliant.

Does anyone know if there’s a fuse I can pull to stop it going off? The unit itself looks unpluggable based off of google images, but I can’t find any information about removing it on a 7.5.

You can definitely just unplug it, here is a guide on how to install the siren, I'm sure it will have the info you need to access the plug.
https://drive.google.com/file/d/1iYUds9Rw_XRlrS8BUHS0KIYPNLaO8kYu/view?usp=sharing

alternatively you can try to just pull the fuse, it is in the engine bay fuse box
https://fuse-box.info/volkswagen/volkswagen-golf-vii-mk7-2013-2020-fuses

Of course, neither of these options really solve your problem...

 

[sicario]

Ah amazing, thank you! At least I can shut it up so I can sleep.

Im highly suspicious now I know the siren unit is under the windscreen… wonder if autoglass cocked something up when they were doing the swap.

Tried pulling engine fuse 20 but alarm still going strong.

All I can think of is that there’s some water ingress that’s shorting the alarm. From what I can tell it only happens when raining (though it’s hard to judge in the UK).

Seems to clear up after a drive, so I reckon either the engine heat or motion is clearing the water. I thought perhaps it was pulling a bit of charge when the ignition was on, but 10 mins idle didn’t fix it, whereas a 10 minute drive did for a while.