Wireless doorbells is another but i dont think many people would be ringing one at 3am

Guy on pistonheads found his new doorbell would unlock his BMW!!!

Interested to hear of problem with the alarm since mine has now triggered a few times since the end of the year for no apparent reason. Different times in different locations so no obvious link to a potential external source that could be responsible.

I will be getting the dealer to check when it goes in for its first service in about a month but don't hold out much hope of an immediate answer. Wireless fob type systems should be encrypted and protected so there should be little chance of external influences affecting the alarm system. The problem is more likely to be linked to faulty internal sensors or software bugs in the control programme.

I will wait to see if anything can be traced.

This doorbell thing might be worth looking into further

Apparently wireless door bells can cause battery drain problems on Range Rovers and you said the car had experienced low batt voltage

Battery Drain on a Range Rover 4.0/4.6

Reading that reminded me of something. I live in a block of low-rise flats and we have a communal car park. I owned a Furby vRS at the time and a neighbour had a 1.4 Fabia. By me unlocking or locking the doors (I can't remember which it was) with the keyfob buttons I could occasionally set off his car alarm. I thought it was just coincidence at first but after I'd done it three or four times I realised I was causing this weird behavior.

He never did work out it was me...

So the question is: Do you have a neighbour that leaves home or comes back during the early hours of the morning and drives something from the VAG family?

Hmm I dont know if this will help , but a guy who lives next to my lock up used to have a Mk5 Golf , and some mornings when he unlocked his Golf with the keyfob , my cars alarm (2000 model year Fabia) would go off , and the cars were around 40 yards apart , and mine was behind a metal garage door! Something to think about maybe??

i am puzzled by all these stories of other cars setting of the alarms . i thought alarms had millions of different rolling codes to prevent this thing from happening. Once maybe, but all the time ?

As i understand it its not that its a specific "code" thats causing the problem but rather the strength of the interference flooding the frequency that the car uses

As i said there was a thread on Pistonheand and a few cars were affected ie BMW's Vauxhalls etc

I dont know if the Superb 2 is the same but i hear my Mercedes sat nav "wake up" as i open the door before i put the key in if outside interference was the issue its possible thats whats happening with your car and the alarm is sensing the current drain

with the faults you have ie the coding changing , car resetting the seat positions etc it leads to think something is being reset in the car when its parked , i do wonder if everything is powering down as it should

As i understand it its not that its a specific "code" thats causing the problem but rather the strength of the interference flooding the frequency that the car uses

As i said there was a thread on Pistonheand and a few cars were affected ie BMW's Vauxhalls etc

I dont know if the Superb 2 is the same but i hear my Mercedes sat nav "wake up" as i open the door before i put the key in if outside interference was the issue its possible thats whats happening with your car and the alarm is sensing the current drain

with the faults you have ie the coding changing , car resetting the seat positions etc it leads to think something is being reset in the car when its parked , i do wonder if everything is powering down as it should

food for thought....i think you have misunderstood the seat issue. it is not resetting the position it is simply refusing to memorise the position once the seat backrest has been reclined beyond a certain point. move the back rest forward and it stores OK.

have people with a columbus noticed the cooling fan running on for a significant time after the car is stopped ? mine seems to run on for ages - maybe 5mins + ?

PS - not loving the fabia experience. what a truly awful tractor engine it has !!:thumbdwn:

Yep i get the seat thing i am presuming the seat has to be set up ie taught its range and that for some reason this range has been or is being reset , i am wondering coupled with alterations to the cars set up ie alterations to the maxidot menu, parking sensors changing if these things are all related , perhaps something is resetting on your car , this process could well set the alarm off as well.

The more issues i see especially WRT your car and the failure of the dealer to sort them the more i get concerned about the arrivial of mine which is expected in 2-3 weeks , i am seriously considering walking away from the order and going elsewhere

Yep i get the seat thing i am presuming the seat has to be set up ie taught its range and that for some reason this range has been or is being reset , i am wondering coupled with alterations to the cars set up ie alterations to the maxidot menu, parking sensors changing if these things are all related , perhaps something is resetting on your car , this process could well set the alarm off as well.

The more issues i see especially WRT your car and the failure of the dealer to sort them the more i get concerned about the arrivial of mine which is expected in 2-3 weeks , i am seriously considering walking away from the order and going elsewhere

rich - i have discussed the issue of the range of the seat with the tech and he tells me he thought the same. he checked the feedback signal from the seat to see if there was a correlation between the zero point and position of the seat (and the max point also). everything stacked up.

the latest on the alarm - a new siren unit is on order (but is on back order !!). I remain to be convinced that this is the problem but worth a try I guess.

in terms of walking away - i seriously have considere where i go next. do i reject the car ? if I do what do I buy ? I am sure other marques have similar issues. I am sure you only hear a concentration of bad things due to being on a forum ! dont let my isues put you off. more and more cars are so reliant on electronics so I am sure they have issues as well.

There comes a point in fault diagnosis where you have to "step back" and look at the bigger picture.

All the systems currently being used to diagnose the system are probably making the basic assumption that the CAN bus is working soundly (at least to an extent). And this might not be true.

There are various physical layers used on CAN Bus. I am fairly sure (I am a telecomms engineer now - I stopped doing embedded stuff 10 years ago), that the one used by VW group is a terminated, 2-wire balanced line.

Given that you are having so many problems, which seem to afflict so many different bits of your car's electrics - there exist two distinct possibilities:

1) One of the controllers is writing crap on the CAN bus - which could cause all kind of problems, "Reset" as recently suggested being one.

2) There is something wrong with the physical bus itself.

Assuming that I'm right and it is a terminated balanced line - then the CAN bus must run as a single pair of wires from a defined starting point (which must contain a "terminator", to each controller in turn, and finally be wired to a terminator at the far end. The two wires carry the same signal - but with one "upside down" (That's what "balanced" means).

One of the good points of terminated balanced lines is that they can carry lots of data, reliably and without corruption - even in an electrically appalling location (like a car).

One of the bad point os a terminated balanced line is that can carry on working, to an extent, even in the presence of a fairly gross bus fault. Like a missing or faulty terminator, a broken bus wire, a bus wired shorted to something else or a controller where the bus transceiver is totally FUBAR.

And I'm wondering if this is what has happened in your car.

Unfortunately, if it were a wiring fault - then even if you replaced every last controller, the fault would continue. And if it is a controller fault, then you could spend weeks trying to find the wiring problem.

As a general rule of thumb, the controllers are actually usually more reliable and better tested than the wiring and connectors.

If you did have a wiring fault, the only systematic way to trace it (beyond searching, searching, searching) is to use a "bus analyser" - which actually looks at the elerctical signals on the line. And you would need to connection to every part of the bus, starting from one termination and working through to the other, controller by controller.

I suspect it would cheaper simply to completely rewire the car. Bus analysers (and the people who know how to use them) are not cheap, are neither is found in garages.

I think AJB1 is definitely on to something here. I've been thinking about this more and more, and the whole thing just doesn't stack up.

Your car has so many deviations from normal, of which the alarm is the most obvious and annoying. A faulty alarm siren as the root cause, simply doesn't explain all of the other odd behaviour.

I went and did some digging on CAN BUS, and AJB1 is absolutely correct about the physical cabling, which when you consider the following:

Fault tolerance

CAN provides a number of fault tolerance mechanisms. One is the inclusion of a 2-bit acknowledgment field. During the acknowledgment time after each packet is sent, the transmitter sends a recessive bit while any receivers send a dominant bit. The transmitter can thus determine that at least one node has received the packet. This prevents a disconnected node from continuing its transmission, blissfully ignorant that no one is listening.

When the bus speed is kept below 125Kbps, the bus can use a fault-tolerant mode where the bus will function if one of the two wires is cut. The motivation for this design is that the bus may continue to operate after a car crash has severed one of the lines. One wire mode is also used if one of the lines is shorted to ground or to the supply voltage. In this mode, noise tolerance is reduced. Each node continues to monitor the faulty line and will resume dual-wire operation if the fault condition goes away.

might go a long way towards explaining your problems.

If your car has gone into single wire fault tolerance mode at any point in the bus wiring, then it will be much more susceptible to interference, which leads to message corruption on the bus, and generally weird behaviour.

However, this still doesn't explain why they can't detect a fault with the diagnostic equipment. Individual nodes on the bus can detect this kind of line failure, and should report it when asked. The only thing I can think of is that the fault is transient, and that the nodes are not keeping a log of the transient failures.

Right now, the garage has gone into 'swap parts and hope we fix it' mode. This could actually make things worse, as you could end in a situation where they replace a working part with a duff one from stores (I've seen this happen many, many times). You are then in an even worse situation.

Personally, I'd tell them to stop clutching at straws, and come up with an action plan that will address all the flaws you've seen. I'd make a list of all the problems, then ask them for an action plan to rectify each one. When they give you this, question it closely. Ask them why they believe the action will fix the problem.

For the example of your car, then one possible question is:

How does a faulty alarm siren cause the alarm to go off at random times?

If they can't tell you, then either get them to go away and find out, or stop them doing it.

If the alarm siren is simply a dumb noise making device i.e. not a canbus node, which simply makes noise when connected to a power supply, then I can't see how this can be the cause. However, if the siren is a canbus device and can receive messages about the alarm from the bus, then it might.

To take this logic further, if the alarm siren is a canbus node, we've got two possibilities:

1) The siren sounds because it's been told to by another device on the bus. In which case, we need to find out why the other bus device triggered the siren, or where the spurious message came from.

2) The siren is faulty, and triggers randomly without any help from the rest of the car.

Ask the garage if they've got a wiring diagram for the siren. Look for CAN-H and CAN-L signals going to it. If you see them, then it's a canbus node. If not, then tell them to stop messing about and actually diagnose the problem.

Bagpuss.

Bagpus & AJB1....thanks for all this, The problem is that I suspect you have gone way beyond the capabilities and understanding of the techs at the dealership. I just about understand what you are saying but then I have a degree in electronics (long time ago and dont work in the electronics field).

I am not sure how much airtime the dealer will give me on this. It feels ike we are all doing their job for them at this point. I am wondering if rejection is the easiest solution at this point ?

i will give it all some thought and let you know what i decide. cheers

Has the dealer been able to tell you what is triggering the alarm. Certainly on my 2003 Passat it would log what had triggered the alarm, this helped me identify a leaky washer pipe in the bootlid which had saturated the boot lock over time.

well - there is an interesting question. The problem they have is they are getting different codes . first couple of times it pointed to a dodgy door sensor which was replaced then it pointed to a low voltage issue - which led them up the misguided path of blaming a reduced charge in the battery. They are now working on the theory that a low voltage is being received by the alarm horn unit due to a faulty horn unit. I remain to be convinced.

what i dont understand is why many of you are suggesting interfernce from and external source. The alarm is not a radio controlled device surely ? its a hard wired unit controlled by the central ECU. any external signals (taxis, doorbells, microwaves have all been mentioned) would not have any effect. surely they are as likey to have an effect on the alarm as they are on ,say, the electric seat or interior light ?

the central locking is operated via a radio wave from the keyfob but this i not directly linked to the alarm. the opening of the doors with the keyfob sets off a chain of events - one of which is the alarm being disarmed. any spurious radio signal in theory could operate the doors but not the alarm in isolation ,surely ?

please correct me if I am wrong but I am just using a logic thought process and cant make the link from a spurious radio signal to the alarm being triggered.

Hi Jonathan,

It's not the control electronics of the alarm system that is being interfered with. This stuff is all well shielded, as the car environment is a very hostile one for sensitive electronics. This is one of the reasons that CANBUS is used. It's very resistant to the kinds of electromagnetic inteference you get in a car.

The problem with most car alarms is the motion sensors. These are the things mounted in the central courtesy light housing, and are usually microwave based. This makes them very sensitive to the kind of radio interference people have mentioned. This interference causes them to think they've sense movement inside the car, and the alarm goes off.

The sensitivity of these sensors can be adjusted, and normally they don't cause a problem.

In your case, this kind of interference is unlikely to be the cause, as the diagnostic equipment would flag up the microwave sensors as the trigger for the alarm.

Bagpuss.

i see !

and also we have had the alarm go off when these sensors were manually disabled (with the button on the B pillar)

If there latest fumble in the dark doesn't resolve it then imho rejection is the only reasonable course of action. As others have pointed out the electrics seem screwed and it manifests itself in many different faults. We are now in April, and you got your car in January. Sorry to be blunt, but it's late

>They are now working on the theory that a low voltage is being received by the alarm >horn unit due to a faulty horn unit. I remain to be convinced.

Sorry - but that line of reason is complete, total and unmitigated ********. Anyone who spouts such crap at you is either bull****ting because they are out of their depth - or bull****ting for some other reason.

----------------

Going back to the facts they are reporting:

If they are sometimes seeing a spurious input and sometimes seeing "low voltage" - then that does suggest a problem with a controller, or the wiring to a controller.

The basics here involve putting away the flashy test gear, printing out the wiring diagram and then checking the supply and all the earths to the module, one-by-painful-one. This process requires someone who actually understand the basics of electronics and fault finding.

----------------

The "interference" thing is nothing whatever to do with Radio control.

Here's some basic electronics. If you want build a very simple (but insensitive) readio receiver, all you need is a length of wire and something which rectifies. Every input to every chip in your car is the "something that rectifies" - and every bit of wire is a "length of wire".

So your car (along with every bit of electronic kit ever made) is stuffed with parasitic radio receivers. This has been a problem with electronics since the dawn of electronics.

Fortunately there are many things which can be (and are) done to reduce the problem. All sorts of methods of making these unintended radio extremely insensitive.

This is all covered by a special branch of electronics called "EMC" (Electromagnetic compatibility).

Many of the methods of avoiding EMC involve having good earths - which is one of the reasons why people suggest checking the earthing.

EMC problems are at their worst when there is a strong transmitter nearby. A police car or Taxis is the worst, with Mobile phone second and then things like doorbells etc.

Finally the "bus" which interconnects all the controllers in your car is called "CAN Bus". It includes some clever design elements which give it good EMC performance.

However, there are faults extant which leave the CAN bus working - but with drastically limited EMC - meaning your CAR bus is far more likely to do something funny any time a radio transmitter comes near enough. Same basic theory applies to earthing etc.

A.

I can fully understand just how frustrating this is for you, but just a thought.....

Have you tried disabling the interior sensor to see if this helps. I say this because I had a problem with an alarm on a Golf and this was found to be a spider in the interior sensor enclosure. At night he would come out and set the alarm off.

As I say, just a thought........

I can fully understand just how frustrating this is for you, but just a thought.....

Have you tried disabling the interior sensor to see if this helps. I say this because I had a problem with an alarm on a Golf and this was found to be a spider in the interior sensor enclosure. At night he would come out and set the alarm off.

As I say, just a thought........

thanks - yes we did this weeks ago as this was our first thoughts. we also had the sensitivity of the interior sensors reduced.

If there latest fumble in the dark doesn't resolve it then imho rejection is the only reasonable course of action. As others have pointed out the electrics seem screwed and it manifests itself in many different faults. We are now in April, and you got your car in January. Sorry to be blunt, but it's late

whilst I agree and am no way defending anyone, i feel that I have had to give them adequate opportunity to solve the issue. I think we have NOW reached that point. One of the problems here is that when they think they have solved the problem it can take a week or two to ascertain that they havent actually fixed it - this is due ot the alarm only going off sporadically. Its not a fault that can be immediately noticed- ie if the wheel bearing was knackered it woudl be obvious as soon as i collected the car if they had fixed it or not. This has obviously delayed things. When a fault was picked up on a door sensor and the sensor was replaced we all believed the fault to be fixed - until 2 weeks later when the alarm went off again.

The new sounder unit was on back order (why ? on a new vehicle ? ) but it arrived on saturday at the local dealers and they are fitting it now. We will hopefully get the car back asap and then sit and wait, with bated breath, and hope the alarm is OK.

If it goes off again then I will be in a tricky position - i will have to take it to the supplying dealer which is 200 miles away for them to look at it. I will not get anywhere with a rejection until they have been given a chance to look at it. although I might be able to argue that since skoda uk central technical have been involved what can the supplying dealer do that my local dealer cant ?

>They are now working on the theory that a low voltage is being received by the alarm >horn unit due to a faulty horn unit. I remain to be convinced.

Sorry - but that line of reason is complete, total and unmitigated ********. Anyone who spouts such crap at you is either bull****ting because they are out of their depth - or bull****ting for some other reason.

i agree, however we need to go though the hoops so i have a water tight case for rejection. If skoda tech are suggesting something and I stop them doing it (ie low battery, faulty alarm horn) it will make rejection hard as they will say I have not given them adequate opportunity to fix the problem based on their (misguided) diagnosis.

I did see the printout from the battery tester to show my battery voltage was below the min and the cold crank test showed the battery to be low also. what could I do in those circumstances - i know in my heart of hearts this is nothing to do with the alarm but they have the hard evidence on paper so i has to run with this theory.

I have been proven right and have received a refund cheque for everything i paid out.

doesnt solve the issue but will help my case i think as i can say they are clearly chasing their tails and dont understand what they are doing

Jon, when you disabled the sensors did you do it electronically or did you tape over the sensors so they couldn't read the air? if you haven't done that method give it a try, it will at least say yae or nae as to if the air is setting them off.

i have the car back now with a new alarm siren unit fitted. its just a waiting game now to see if the alarm goes off. i will make sure my keys are near me all the time and will try and make a note of the time and circumstances if it does go off.