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Model specific boards => Golf mk6 => Topic started by: Borbus on 17 January 2021, 21:25

Title: Alarm randomly going off
Post by: Borbus on 17 January 2021, 21:25
Twice now my alarm has randomly gone off. First time was in a car park. When I came back the hazards were going off. I assume the siren/horn had stopped sounding by that point. Happened again today at home. This time the siren was going off so I could hear it.

I've read a few places online that it might be the siren going bad. That's a £150 part and needs drilling out  :sad:  Are there other possibilities? Anyone dealt with this?
Title: Re: Alarm randomly going off
Post by: Snoopy on 18 January 2021, 11:00
Ultrasonic sensors go faulty.
Try turning off the interior sensors and see if it does not false alarm.
Bonnet switch.
Have read they can go faulty.

If its the siren or theres a fault on alrming. The led on the door will flash a sequence when you arm it to tell you there is a fault. Cannot remember how many flashes meen what. But I did see it online many years ago. A google search should find the info.
Title: Re: Alarm randomly going off
Post by: Borbus on 18 January 2021, 17:27
Interestingly I did open the bonnet just before the most recent false alarm. I didn't realise there was a switch under there. Hopefully just gone stick or something. I'll check the LED next time I lock it.
Title: Re: Alarm randomly going off
Post by: Borbus on 23 January 2021, 13:59
OK so it went off again today. Both times when I was at home. I had parked it away from home twice, but maybe not for that long, and it was OK. At home it has now gone off twice. After about 30 minutes after locking it I would say.

The LED on the door does flash quickly, 7 times, before it goes to normal. Can't seem to find what this means online, though.
Title: Re: Alarm randomly going off
Post by: Borbus on 23 January 2021, 14:30
OK, so I'm showing several codes about alarm horn being faulty, so I guess that's it.

Trouble is it's now going off every few minutes. Any ideas how to disable the alarm completely? I've resorted now to just no locking the car, but I've a feeling it will lock itself before long. If I can't figure it out I'll have no choice but to disconnect the battery until I can get this alarm horn replaced.
Title: Re: Alarm randomly going off
Post by: SRGTD on 23 January 2021, 17:38
I owned a Vauxhall many years ago where the sounder / siren had an integral back up battery that failed while the car was under warranty. The alarm would go off shortly after locking the car, and the only way to silence it was to leave the car unlocked (fortunately, I garaged the car, so it wasn’t left unlocked in full view of others). The sounder / siren unit was replaced under warranty and didn’t cause any more issues.

I don’t know if VW alarm systems have a similar back up battery but if they do, maybe that’s the cause of your problems. Also, is your 12v car battery in good health? With many cars being used less during lockdown, if your battery isn’t holding its charge through lack of use, then could that be the reason your alarm is sounding?
Title: Re: Alarm randomly going off
Post by: Snoopy on 23 January 2021, 19:01
Did you try turning off the ultrasonic interior protection with the button. Temp changes set these off if yhey are starting to fail. Would explain the time before false alarm
Title: Re: Alarm randomly going off
Post by: Borbus on 24 January 2021, 14:22
I did, yeah. I tried both with the interior button, and by pressing the key fob twice (not sure if this actually does disable it, though).

My battery is showing 11.7V in OBD11. I assumed this was fine as it always starts fine and no other problems. But just reading about it now and it seems the voltage shouldn't ever be below 12V. Will test the voltage with a multimeter now...
Title: Re: Alarm randomly going off
Post by: Borbus on 24 January 2021, 14:54
OK, so the voltmeter shows 12.2V at rest (it's about 0 degrees today).

10.4V minimum when starting and 14V while idling (both seem normal).

12.2V is a little low... The battery says min 12.4V on it. Low enough to cause this, though? I do hope so as changing the battery is easy.

I can't see any record of it being changed. It's a Bosch S4 005. Is that the original?
Title: Re: Alarm randomly going off
Post by: Snoopy on 24 January 2021, 20:25
As reference. My leons siren went off today when i tried to start it with a low battery as ive only used it once this month. So I would say if the voltage drops low it seems to set the siren off probably using its own battery backup.
So maybe.
Title: Re: Alarm randomly going off
Post by: Borbus on 09 February 2021, 17:00
I've had my alarm siren module removed. A new module would have cost ~£200 and I was extremely loathe to pay this as I find alarms stupid and pointless anyway. So I've just had it removed and now it's all fine. The alarm doesn't go off randomly. The car is still technically alarmed and the hazards will flash if the alarm goes off, it just won't make a sound. Fine by me!

The module itself is completely sealed up and impossible to get in to. I reckon it's probably just the NiMH battery inside that has failed. Could probably just replace that and fix the problem, but it's been designed to be non-serviceable. I really hate that. No reason for it.