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Info guides and mods

Baby Seats

There is a lot of conflicting information about the fitment of baby seats

Modification Details

 If you talk to someone in a smart dealer about baby seats, they will almost certainly tell you 1 of 2
things. The most popular reply is usually "I don't know, I'll get back to you on that". On which they
invariably don't. The second is that the only suitable baby seat for the smart is the smart baby seat.

This is, in fact, wrong. It's a standard sales technique that scares new parents in to paying the
extortionate price for the official seat and airbag deactivation switch or a replacement Mercedes.

The truth is that the official smart seat is the only recommended rear facing baby seat.

The Airbags

If you have seat side airbags you MUST use the official smart baby seat.

The obvious reason for the rear facing smart baby seat deactivating the passenger airbag
is that the back of the seat falls within the range of an inflating airbag. You obviously don't
want the seat being touched by the airbag as it goes off.

However, unless you see a smart airbag, you would immediately assume that it comes towards
you to cushion the impact. It doesn't. It inflates up and over the dash to protect unbelted
passengers from hitting the dash or the windscreen. It also protects the passenger from any
of the windscreen should it break so you won't get showered in broken glass.

Forward Facing Baby Seats

If you have seat side airbags you MUST use the official smart 
baby seat unless you deactivate the passenger airbags fully.

Almost all forward facing baby seats are suitable for the smart as long as they are secured
properly. All good forward facing seats come with the relevant fixings required.
If you aren't 100% confident then consider getting it fitted by a professional.

With the forward facing baby seat fitted, the airbag clears the seat and the baby by a long way.
The bonus of keeping the airbag activated is the protection from broken glass mentioned before.


Smart rear facing seat or almost any forward facing seat.
The airbag emerges from under the dash, goes over the dash and covers the windscreen.
If you have seat side airbags you MUST use the official smart 
baby seat unless you deactivate the passenger airbags fully.


Smart rear facing seat or almost any forward facing seat.
The airbag emerges from on top of the dash and covers the windscreen.
If you have seat side airbags you MUST use the official smart
baby seat unless you deactivate the passenger airbags fully.


The Forfour has rear seats so is suitable for all baby seat setups in the rear.

Rear Facing Baby Seats

From birth to approximately 12 to 15 months, it is essential that you use a group 0 or group 0+ seat.
These seats are rear facing as they offer more support to your screaming pink bag of poo baby in a crash.

With a rear facing seat, it is essential that the seat side airbag (if you have one) and the passenger airbag is off.

Deactivating The Airbags

When the smart child seat is installed, extra wiring and a switch is added to the car.
Adding the seat trips the switch and deactivates the passenger airbag.
When you start the car, the airbag light flashes a few times to let you know it's deactivated.

There is an alternative shown in the WIS manual, it is a kit with an extra keyhole that attaches
to the front of the SE drive cover. However it seems to be a Canadian part only.

The final way is a bit of a bodge. You can disconnect the airbags and short circuit the connector
with a resistor of a set rating. The car checks the airbags by monitoring the resistance on startup,
so adding these resistors fools the car into thinking the airbags are still connected.
Given the possible outcome of this mod I will not be giving out the resistance required.

Do not, under any circumstances, just disconnect the passenger airbags.
It will cause an error in the airbag controller and ALL of the airbags will be deactivated.
Even if you then plug the airbags back in, they will still be deactivated.
You will have to go to smart dealer or smart specialist to have the error code erased.

I know that none of you have actually read the site disclaimer so considering the topic I
thought it prudent to totally cover my arse on this matter.
If you follow any information on this page then it is of your own doing, I do not take any
responsibility if you set off your airbags, the error light comes on or an infant is killed.
Drive safely, keep looking forwards and hope you never have to rely on the airbags.

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