MB alarm, false triggering?

[philharve]

Hi All

I have owned my W202 almost 4 years but today it did something that it has never done before, its security alarm sounded, apparently for no reason. My brother was witness to the event and he swears my car was not being interfered with. The alarm was spontaneously activated and the lights flashed. My brother said that there were no other vehicles close to my parked & locked car and the only sound he heard was another car engine being revved about 50 yards away behind a building. The weather was dry and the temperature was about 14 degrees C.

This singular event raises a number of questions to which I would appreciate some answers or at least advice.

1 - Do MB security alarms sometimes respond to external stimuli such as sound vibrations emanating from machinery, e.g. other vehicle engines? I have never known it happen to my C230K before.

2 - My brother reported that the lights stops flashing some time after the horn stopped sounding. Is this the normal sequence? Other vehicle alarms I've witnessed resetting usually switch off the horn and extinguish the lights together. Is there a reason for staggering the resetting of horn & lights?

3 - This may seem like a daft question but what conditions trigger the security alarm? I have an orientation detector that detects whether the car is being raised prior to illegally towing away and I assume that breaking any of the glass panels will trigger the security alarm. Is there a vibration or sound sensor onboard? What about detecting the tampering of the door locks, boot or fuel filler cap? I was wondering if radio frequency interference (co-channel) operating on the same frequency as used by the key fob could trigger the alarm?

4 - Is there a list of the security sensors fitted to modern Mercedes vehicles somewhere?

I would like to get to the bottom of why my car alarm activated for no apparent reason after almost 4 years and whether it is likely to happen again. I've never experienced any electrical gremlins with this car and the only time it let me down was when the battery developed a dead cell which was easily rectified. I don't believe the weather had anything o do with it either. What does this leave? A singular event that will never happen again!

REGARDS

Phil

 

[Cole@MBS]

Phil, if you really want to know what triggered it a star test can tell you, the siren fitted to your model is prone for water ingress, wouldnt be a bad idea to remove the plug and check its not green on the plugs!!

 

[philharve]

Hi S-A-M / U-N-I-T

Thanks for that advice. I have made a note of your suggestion and noted the event in my diary. I will discuss this matter with my indie when I next visit him, probably this coming Wednesday. Would a Star Test pinpoint what caused the alarm to trigger or would it be restricted to reporting what sensor was activated?

I will also bear in mind your suggestion that it might be caused by the ingress of damp.

REGARDS

Phil

 

[Cole@MBS]

Yes, thats right, you can go in and see what the last alarm occurrence was caused by, i,e alarm siren, door pin, and so on, as i said before, your model does suffer from water ingress, easy to trace that one!!

 

[philharve]

Hi S-A-M / U-N-I-T

I tend to think it was due to damp because now I'm retired I don't use the car so much nor do I do the miles. It could be 3 or 4 days between using the car and with the poor weather we've had recently, dampness may have entered into places where it has caused the alarm to sound. It seems like one of those rare conditions that may not happen again for a long time. However, I will check with my indie just in case. I don't want the alarm sounding at odd times during the day, or worse, at night.

REGARDS

Phil

 

[Cole@MBS]

That could be one of the problems Phil, if the car is sat around, in these damp and salted times, it dont take much once the damp has got into a plug connector!!

 

[television]

I go along with the siren as SAM

Now I know what your car is phil, I will sort you out the suspension details

 

[Stu_CDX]

I can answer something about the lights

The hazard warning lights flash on for longer so people are made aware that the car has been interfered with without being deafened. Again, as mentioned in different threads, it's something my old Cavalier used to do. Was a little annoying tho as only one side worked. The drivers side ones wouldn't flash if the alarm was going off!

 

[philharve]

Hi Stu_CDX

Thanks for that feedback. I deduced that the reason the lights flashed for longer was because the horn would soon becoming annoying. My previous was a Toyota an the lights & horn operated together.

REGARDS

Phil

 

[philharve]

I go along with the siren as SAM

Now I know what your car is phil, I will sort you out the suspension details

Hi Malcolm

This will be WRT my inquiry concerning the front wheel alignment on European and UK cars? My cars are mentioned in my signature, latest first.

The reason for this particular inquiry is linked with the steering problems I raised in other threads. I seem to recall from years ago that the toe on front and rear driven cars maybe different. It has to do with torque and grip causing the tyres at assume a particular alignment as speed increases. It was something like, 'front-driven cars have toe-out because as speed increases the tyres tend to adopt a more straight ahead direction when transmitting power; and rear-driven cars have toe-in for the same reason except they are not transmitting power: the rear wheels are 'pushing' the car. If you see what I mean? I may have got it the wrong way round though.

I have this nagging feeling that the suspension of European cars are setup differently to UK cars because road speeds on the continent are generally higher. The degree of toe in/out involves a compromise between speed, wear and handling. Would a UK car handle less well on the autobahn than one setup for the autobahn?

Of course none of this has anything to do with this thread concerning 'false alarms' but I added this explanation so you know what's on my mind.

REGARDS

Phil

 

[philharve]

Linyphiidae

Hi All

I visited my indie today to inquire about the false alarm my car experienced last week. He said that 9-out-of-10 times it's due to Linyphiidae. He added that if he plugged the car into a Star Tester it would almost certainly report that the alarm was triggered by the interior infrared sensor.

Linyphiidae, of which there are around 250 species in the Uk, is a micro-miniature spider of which the most common is called the Money Spider. They crawl into dark places and build their nests and webs. In a W202, like mine, one of the favourite homes for the Money Spider is behind the covers that hide the interior infrared security sensors. These 'rounded, triangular' covers are located inside the car at the top of the 'B' pillar (near the roof lining) and above the front seat safety belt anchor points.

These covers can be removed with the finger tips and behind them are pairs of infrared transmitters & receivers. The space around the transmitters & receivers should be vacuumed to remove the Money Spiders, their webs and their nests, because it is the movement and web-building activities of these little spiders that break the infrared beams and sets of the security alarm.

Very occasionally small flying insects can get inside vehicles via their ventilation systems and once inside they can interrupt the infrared beams. However, the beams are most sensitive nearest the sensors themselves.

My indie advised looking under the covers as the first step to troubleshooting the false alarms. He thought the likelihood that damp affecting the electrical conductivity of the wiring/components of the security system was highly unlikely unless the vehicle has suffered from defective wiring and/or components before.

If the false alarms are caused by Linyphiidae, it is likely that the false alarms will increase unless the growing colony is evicted.

REGARDS

Phil

 

[Cole@MBS]

Why didnt he just run a star test Phil, that would have told you stright away what caused the alarm to sound instead of guessing???

 

[television]

There are modified sensors for some cars

 

[philharve]

Vacuum cleaner at the ready.

Hi S-A-M / U-N-I-T

Two things: my car was parked up in a multi-storey car park about a half mile from the indie's premises; he was busy on another job but said a test would almost certainly prove him correct. It is an extremely common problem that sometimes result in unnecessary and expensive repairs being undertaken. Most owners tend to think the security system has failed when in fact it is one of the most reliable systems on the vehicle.

He advised I took a look under the sensor covers and vacuum the space around and between the sensors.

He said some people place strips of black tape over parts of the sensors which reduce their sensitivity to 'bugs'.

Alternatively the sensors can have a software upgrade (I didn't believe it either) to reduce their sensitivity to spider movement but at a cost of GBP150.00 most owners prefer the vacuum cleaner solution.

I gave him the last of my Christmas cards and thanked him for his honesty.

REGARDS

Phil

 

[Cole@MBS]

Phil

Im not knocking the chap and didn't know your car was in a car park, not the normal place for a sorting out car problems, as for the software update, well you answered that yourself!

 

[philharve]

Naphthalene or Paradichlorobenzene

Hi All

I have just spoken to a colleague who is a bit on a expert on little crawling & flying things and he stated that Naphthalene (Moth Balls!) could be placed beneath the sensor covers and the vapor given off will deter the Money Spiders from taking up residence and kill of the microbes that they feed upon. A Moth Ball cut into two pieces should provide protection for 6 - 12 months for both sensors.

The only question is whether Naphthalene (or Paradichlorobenzene) is likely to react with the delicate sensor circuitry.

REGARDS

Phil

 

[television]

During my 3 years on this forum we have had 2 other cars with money spiders setting off the alarm,, one was a 210, possibly Parrot or malcolm210

 

[philharve]

Is integrity disappearing?

Hi Malcolm

Your observation poses some interesting questions, the uppermost in my mind being, how many of the alarm faults that have been reported in this forum were actually caused by infestation but were attributed to some form of electrical failure by those investigating/repairing to fault?

I have acquired a cynical frame of mind of late because the chance to make a profit often proves to irresistible to miss for some.

My indie informed me that he considers it his duty to seek ways to reduce the costs of Mercedes ownership and if a simple solution exists to take it. His repairs are undertaken using Mercedes parts & procedures but he often supplements them with procedures of his own, including investigating possible Money Spider infestations.

Is integrity steadily disappearing from the repair workshop? Maybe the priority to show a fat profit is the deciding factor.

REGARDS

Phil

 

[roofless]

it's also possible he was busy & cant afford the time so fobed you off with the sight unseen spider theory ?

 

[television]

Well Phil the post that I put up here about modified sensors applies to your car, I have printed off for you. It say when the alarm goes off when the car when the car is locked for a longer period of time

I am just looking at the wheels set up and I can send that as well