Alarm goes off - even when not primed: S210

[4 Strings]

It's stopped for today so urgency calmed a little, but the alarm would go off every couple of minutes.

Slammed the doors, looked for spiders etc, could not solve it. Anyone else have this?

I noticed led on the tilt sensor/interior sensor disable switch was flashing slowly. This has now stopped.

Also, I noticed a yellow light on the underside of the mirror which comes on with the ignition. What does that signify?

Couldn't find anything in the handbook, any hep greatly appreciated.

 

[Auto-mobile]

Led will flash, yellow light is your ambiant lighting, I recommend replacing your alarm siren.

 

[Abb]

It will more than likely be the actual alarm siren. It houses a small battery on the pcb, which often leaks due to age/time and begins to randomly activate the alarm.
Happened on my fathers 05 S320 earlier this year, replaced siren, no more false alarms!
IIRC they are approx £100 from MB.

 

[4 Strings]

The yellow light is a very small light (around 10mm) on the bottom edge of the mirror. You don't see it under normal conditions but hold your hand under there and you can see it reflect. I wondered if it's signifying a fault.

The alarm only goes off when it's parked. Did it again tonight a few times. Never goes off when driving so if it was a battery leaking it would go off at any time.

(Ridiculously, my last car, a C200k, also had the same problem, just randomly did it for a few days then ok for months.

 

[whitenemesis]

You describe exactly how the ambient light performs, it not there to illuminate the interior but your hand as you reach over the centre console.

The alarm module won't go off when driving as it's not been put into circuit. It's classic alarm failure symptoms.

 

[4 Strings]

Really? It's yellow and not bright/large enough to illuminate anything (only your hand if 10mm away!). Well, if that's what it is it's pretty poor!

The other thing with the alarm is it only seems to go loopy at night (of course, the most annoying team for everyone!). Don't know if that helps with the diagnosis.

 

[Dec]

As already stated the alarm is faulty and needs to be disconnected, you can if you wish replace it with a new one from an MB dealer, cost around £100.

The alarm siren is the brains of the alarm system, it has its own power supply in the form of 7.2volt rechargeable batteries.
When you lock the car, with the remote, you also arm the alarm and the cars 12 volt battery replenishes the 7.2 volt batteries inside the alarm.

After about 10 years the rechargeable batteries degrade, as can be seen in the picture above and usually damage the alarm siren PCB.

For now, if you lock the car manually, with the key blade, then the alarm won’t be armed and should not go off in the night.

Dec

https://www.youtube.com/watch?v=zChaQHHaeJU

[YOUTUBE]zChaQHHaeJU[/YOUTUBE]

 

[4 Strings]

Yuk, thanks!
Where is this located on a 210, please?

If this was the issue it would go off equally during the day as well as the night, wouldn't it?. Mine exclusively got off at night.

 

[Dec]

Perhaps night time temperature or time play a part, how long after you lock the car with the remote before the alarm sounds?
If it’s not going off during the day, could it be that the car isn’t locked during the day with the remote or isn’t locked for any great length of time?
The video in my last post shows the alarm siren location, I presume your alarm is located on the driver’s side but you will hear which side its on when it next sounds off.

Dec

 

[4 Strings]

Thanks, Dec, I'll have a look. At the moment it's behaving itself so the urgency has reduced - until the next time!

It's sits outside during the day as good as gold, just waits until the night to annoy everyone.

Is there any reason for the slow flashing light tilt sensor/interior sensor disable switch?

 

[Dec]

When alarm armed, it flashes 60 times a minute, is yours flashing 30 times a minute by any chance?

It could be that it’s trying to let you know its not well.

Dec

 

[4 Strings]

When alarm armed, it flashes 60 times a minute, is yours flashing 30 times a minute by any chance?

It could be that it’s trying to let you know its not well.

Dec

Haha, I'll go and have a count!

I wondered if it was trying to tell me something, does it slow if there's a fault?

 

[Dec]

I don’t know, I’ve hear it said before that it can flash slowly so was wondering if it is to indicate a fault if it flashes at ½ the normal speed.

Dec