Car alarm going off randomly (Urgent help required please)

[jonnydarcy]

Hi,
my car alarm is going off randomly, tellingly without the accompanying indicator lights flashing. Having read around it looks like I am having the very common problem of water from the rear wiper pipe feed leaking into the boot lock mechanism and causing a fault in the microswitch.

I tried to remove the rear plastic in the boot to get access to the mechanism but I wasn't able to work out how to do it. I removed 2 screws in the plastic (the only ones I could see) but wasn't sure which way to pull/push etc. Can anyone direct me as to what i need to do in order to be able to get to the boot microswitch

In the interim, is there a way to disable the alarm? Can I just disconnect the battery? The car kept my neighbours up overnight and I won't get a chance to fix the problem until later in the week so I must disengage the alarm ASAP!

Thanks for all help

 

[<tuffty/>]

Alarm unit is in the boot... there is a thread in the FAQ's for replacing the battery's in the alarm that will help you locate and unplug the siren

You would also be advised to scan for fault codes using VCDS as the alarm unit and alarm triggers are logged as faults... this should help the diagnosis...

There is a reason the alarm is going off and this might help pinpoint the issue

<tuffty/>

 

[jonnydarcy]

Thanks Tuffty. Pretty confident the issue is water in the microswitch, not least as a few weeks ago I noticed the rear water jet on the rear wiper wasn't working properly (implying a leak).

 

[sirbobalot]

Alarm unit is in the boot... there is a thread in the FAQ's for replacing the battery's in the alarm that will help you locate and unplug the siren


You would also be advised to scan for fault codes using VCDS as the alarm unit and alarm triggers are logged as faults... this should help the diagnosis...

There is a reason the alarm is going off and this might help pinpoint the issue

<tuffty/>

I agree I had the same problem but I just unplugged mine as it is a sealed unit and didn't want to hack it apart. Have been trying to find a second hand one since but no luck yet.

 

[jonnydarcy]

Is disconnecting the battery an option? I'm not using suing the car much at the moment.

 

[sirbobalot]

Is disconnecting the battery an option? I'm not using suing the car much at the moment.

No the alarm unit has a built in battery that is dying that's why it keeps going off the only way to turn it off is to unplug it or just leave it till the battery has gone but that could take a while.

 

[jonnydarcy]

Ok thanks, I must say I had assumed the alarm had its own dedicated power supply for security reasons.

Just to clarify, I don't believe the alarm is dying. As posted above, I believe this is a malfunction due to a leak. Happy to have my diagnosis corrected of course.

 

[sirbobalot]

The alarm does have a built in battery as its supply but these tend to fail and cause the problem you are having bit if you think its the switch get a hair dryer to the boot latch and try and dry it out if you keep getting the same problem after then you have a alarm battery problem.

 

[<tuffty/>]

You can unplug it while unlocked then lock the doors with the key... this shouldn't set the battery backed part of the alarm off... I have left my car for weeks with the battery disconnected before now will no issue

<tuffty/>

 

[jonnydarcy]

Agreed, great, thanks.

 

[jonnydarcy]

Anyone with a steer on how to remove the boot cover to get to the rear wiper and lock mechanism?

 

[SamHendry]

Anyone with a steer on how to remove the boot cover to get to the rear wiper and lock mechanism?

I had to remove this cover to do my rear wiper delete. Couple of screws as you mentioned and there is clips hidden behind the plastic. The plastic just pulls away from the bootlid. I used my hands to pry it from the lid, you do need to apply a bit of force but so much it breaks

 

[s3kirk]

I had to remove this cover to do my rear wiper delete. Couple of screws as you mentioned and there is clips hidden behind the plastic. The plastic just pulls away from the bootlid. I used my hands to pry it from the lid, you do need to apply a bit of force but so much it breaks

exactly that! ^^^ had mine off in the dark yesterday trying to change my number plate light housing, nearly broke mine as i didnt see at first there was 2 screws in the grab handle. prise it back starting from the bottom of the window, i found this to be easier than starting from the bottom of the lid.

 

[s3kirk]

also dont loose the 2 square tabs that slide onto the bottom of the plastic, took me about 15 minutes to find mine in the dark as they pinged off when you pull the trim off the boot.

 

[rupe]

Here's a pic of the back of it so you can see where the clips are if it helps at all. I got myself a nice black nail removing that after pulling it away and it slipping back and trapping my finger, so try to avoid that

 

[jonnydarcy]

Thanks rupe.

I forgot to also add that over the last 4-6 weeks I've noticed that the DiS has occasionally been showing that the boot is open when clearly it's shut. The waterlooged (or faulty) boot microswitch is surely the culprit.

 

[rupe]

Sounds about right the connections are very poor, mine came apart behind the battery in the engine bay, fixed that and then it came apart behind the subwoofer, fixed that and then it came off the wiper motor itself and I repaired that using a small piece of washer hose a cable tie and some electrical tape.Have had to repair my mums vw polo in a similar fashion, as that one was the same too.

 

[jonnydarcy]

Morning all. So the local garage took a look yesterday and found no issue. No leak from rear wiper water feed, no corrosion, no water in microswitch. They've given it all a clean and dried out everything anyway. Car was reconnected yesterday lunch time and so far no alarm. I can't say I'm too confident though. Perhaps it's just a failing microswitch.

Thanks for all your help, much appreciated.

 

[jonnydarcy]

Irritatingly the alarm is back...

 

[jonnydarcy]

Just been talking with my garage about when they can take my car in. Looks like it might not be for a day or two...

Just a thought but if I assume that the reason the car alarm is going off is because the system thinks the boot is open (i.e. that the boot microswitch is the problem whether water damaged, corroded or just faulty), can I not simply disconnect the electrics to the boot switch?

 

[jonnydarcy]

Anyone able to help?

 

[<tuffty/>]

No sure if the alarm activates if you disconnect the boot switch... it will still lock and the immobiliser will still work but I know if I arm mine with a door open it won't beep... normally means the door hasn't shut properly

<tuffty/>

 

[jonnydarcy]

That's a possibility, thanks Tuffty. I guess it would make sense that if the car isn't receiving information about whether the switch shows as open or closed it might take the conservative view and consider the boot open (and sound the alarm).

Having said that though, when I disconnected the main battery for a few days last week the alarm didn't sound at all (as far as I know) and given what you have said, I would expect that having no main battery might have had the effect of setting the alarm off. This makes me think perhaps with the switch disconnected it assumes it to be closed.

Hmm (strokes imaginary beard)

 

[<tuffty/>]

If the alarm wasn't set when the battery was removed I wouldn't expect it to go off tbh...

A failing battery should cause the alarm unit to give 3 beeps from the rear when you turn the ignition...

<tuffty/>

 

[Tooks]

That's a possibility, thanks Tuffty. I guess it would make sense that if the car isn't receiving information about whether the switch shows as open or closed it might take the conservative view and consider the boot open (and sound the alarm).

Having said that though, when I disconnected the main battery for a few days last week the alarm didn't sound at all (as far as I know) and given what you have said, I would expect that having no main battery might have had the effect of setting the alarm off. This makes me think perhaps with the switch disconnected it assumes it to be closed.

Hmm (strokes imaginary beard)

If the garage found no fault with the boot microswitch etc, I'd be more inclined to look more closely at the alarm unit.

Yes, you're getting an occassional DIS display that states the boot isn't closed properly, but that could be a separate and independent fault. They are prone to it at this age!

All 3 of my last VAG cars from the 2000+ era, and my father in laws 2003 plate A4 Avant, have all had leaking batteries in the alarm siren unit giving ghost activations. Fixing that along the lines of the guide in the stickies and/or replacing the unit has solved it. In only 2 of those last 4 cases have there been any warning beeps to show the batteries were going west.

I managed to repair mine in all 3 cases, but I like soldering and the battery leak hadn't damaged the circuit board too far, but my father in law had to replace his siren as it was too far gone.

 

[jonnydarcy]

Thank Tooks, that's goo insight. Scraping the codes (which hasn't been done yet) should hopefully give a steer on the problem. The back of the car certainly looks in good nick. I pulled off the boot panel and everything looks like it's just come from the factory. No obvious signs of leaking/corroding there at all. Given how randomly the boot open indicator on the DiS has appeared it naturally feels more likely to be the root cause in some way. For example the car can go several days without the alarm going off.

Helpful post though Tooks, thanks.

Car is off to the garage tomorrow.

 

[Broken Byzan]

A vcds scan will confirm which switch is setting it off