Passenger airbag with kids booster seat

[davidjpowell]

Had a 'discussion' with SWMBO tonight, as she has been putting the little one who thinks she is old on the Front passenger seat, with her Booster seat.

Argued that she is too little still should the airbag go off etc... She says' it switches itself off.

Much confused, as being adamant that it could not, without the MB transponder I went to demonstrate, and was proved wrong.

How the heck does it know? I am really confused and mildly impressed.

 

[GordonTarling]

The airbag won't fire if the seat is unoccupied, so your child's weight is insufficient to make the car think there's someone in the seat.

 

[davidjpowell]

Nope don't think that's it. When she is sat on the seat, and only when the seatbelt is bucked, the airbag disarmed light illuminates.

If she was too light, it would not illuminate - or would it? Is there some sort of logic that if the weight is not big enough and the seat belt is fastened the light come on. In which case why do you need to buy the £350 baby seat with a transponder for a modern Merc?

 

[Diesel Benz]

The weight sensor (seat occupancy sensor) is intended to detect if an adult is present or not. The sensor would not be accurate enough to switch off the airbag for a kid, specifically if the small kid sits on a heavy baby seat. MB does not compromise safety, specifically with kids.

 

[davidjpowell]

But it does!

 

[Diesel Benz]

But it does!

You mean according to your exhaustive tests with kids of different weight and type? Or are you saying the sensor was after all designed to accurately recognise which kid can handle the airbag? I think I did not understand your point.

 

[davidjpowell]

My very exhaustive test I will have you know

My point was that I always understood that the only way the airbag was disarmed, with the disarmed light illuminated was with the MB Baby / booster seats with the transponder fitted.

I don't think I have ever seen anything on this site otherwise, but clearly something is different...

 

[GordonTarling]

There's definitely an occupancy sensor for the front passenger seat, but just how the logic works is a bit of a mystery, it seems. Perhaps a call to a dealer's service department may shed some light on it? (or perhaps not!)

Thinking about it - maybe if there's no-one in the seat and the seat belt is unbuckled, then the airbag isn't armed, but you don't need to know about it, so the light stays off. If the seat belt is fastened, then maybe the light is telling you that the seat IS occupied, but no weight has been detected on the seat - maybe a fault.

 

[corned]

Occam's Razor

No logic or clever technology here! The simplest answer is usually the correct one. Our child booster seats do exactly the same thing. No transponders or fancy stuff like that in the seats.

The reason that the airbag is disabled with this cheap booster is that the base of said booster straddles the central seat squab and therefore no weight worth mentioning is applied to that part of the seat.

Therefore the pressure sensor is not triggered! Simples!