[laluks]

Originally Posted by SS-Traveller

It's actually a chemical reaction.

Air bags are actually inflated by the equivalent of a solid rocket booster. Sodium azide (NaN3) and potassium nitrate (KNO3) react very quickly to produce a large pulse of hot nitrogen gas. This gas inflates the bag, which literally bursts out of the steering wheel or dashboard as it expands. About a second later, the bag is already deflating (it has holes in it) in order to get out of your way.

HowStuffWorks "Airbag Inflation"

Found some more relevant material about airbag checks. Please take a look:
Howstuffworks

Use of Sodium azide was popular in some of the airbags. Since the chemical reaction releases traces of sodium it is considered to be harmful and new compounds are being used to avoid this.

The compound is kept enclosed in a small enclosure along with a heating element(usually looks similar to SL100 transistor), thermally shielded, and on the top of this we have the bags which are semi porous.

The moment a deployment is initiated currents of about 1.5 to 2 amps is sent to the heating element of very low resisitance to initiate the chemical reaction. Heat is the catalyst here. Normally the heat generated is above 120 degrees to initiate the reaction. The car can be as hot as X degrees or so, plus some safety band - that's how a 120 degree plus heating point was found, so not as to trigger unnecessary deployments. Further it is also the reason for thermal shielding.

Normally the airbag ECU will check this resistance every few milliseconds as part of its checks. If there is a short, or open then the ECU will log a corresponding fault and warning lamps will blink. Hence if there are no warning lamps - you must just believe the system.

Coming to the point raised in the thread start, can I fool the ECU. answer is Yes and NO. Just a short of the sensor wires will not fool the ECU. You must fool him with the resistance value he is expecting - but that a normal end user will not know for sure.

Further - if all you want is to see a deployment, remove the steering with the airbags and connect the 12 volts from the battery to the airbag unit in the steering. It would be advisable to keep a long wire and steering far away before you connect to the battery It will deploy for sure!!

Originally Posted by GTO

Standard airbag installations are usually good for atleast 10 years from leaving the factory. Of course, it isn't idiot proof and someone determined could mess around with the sensors. As long as your choice of service center is trust worthy, you have nothing to worry about.

Normally all airbags components are made to withstand the normal life of a car. The philosophy here is that it should never get used till the car life is over, but in the case of a use it must never fail too. At the end of the life of the car, due to environmental laws prevalent, all airbag installations in the car will be forcefully deployed through commands sent through the OBD ports before junking!

[ImmortalZ]

Nice post laluks. Airbags are one of those things we must just learn to trust.

[anupmathur]

Originally Posted by laluks

Further - if all you want is to see a deployment, remove the steering with the airbags and connect the 12 volts from the battery to the airbag unit in the steering. It would be advisable to keep a long wire and steering far away before you connect to the battery It will deploy for sure!!

Nice post Laluks. Thanks.

The testing part is very interesting. So how often would you recommend the test be done? Hope it is not too expensive!

[cool.aquarian]

Apart from when they come into use, what other times do Airbags need replacement.
I asked a friend of mine, why Indian cars sometimes offer ABS as option, but dont offer Airbag as option.
He answered that the Airbags on our Indian Cars need replacement after 8 months if they are not used by that time, otherwise they wont get inflated when required. He also added that only Airbags of some higher segment premium cars have longer Airbag replacement (2 yrs max).

Is it true ?
I am ignorant of anything related to Airbag maintenance.
Please Help me.

[GTO]

Originally Posted by cool.aquarian

I asked a friend of mine, why Indian cars sometimes offer ABS as option, but dont offer Airbag as option.

Cost, cost, cost and only cost. Airbags can push up the price of a car by a minimum of 50,000. A majority of the price sensitive Indian market won't be willing to pay for this.

He answered that the Airbags on our Indian Cars need replacement after 8 months if they are not used by that time

Not used in 8 months? Does he expect each new car to have atleast one airbag-activating accident every 8 months? Please disregard your friend's answer.

Read through this thread. Some great posts on the life of an airbag.

[ksethuram]

Manufacturers in the 90's used to recommend checking of airbag after 10 years. I remember somewhere reading that it has been increased to 15 years in this decade.

Replacement after 8 months

The mathematics does not add up.
I suppose it may be a marketing tactics from a dealer whose lineup do not have cars with airbag.

All modern cars with airbags have internal routine checks done by the ECU. the airbag or SRS light will stay on if anything is wrong. Even then it is good to check it every 10 years. I would rather spend the money in checking it rather than discover a malfunction in the event of an accident.

Meanwhile, Ford has brought in new airbags for rear seat passengers where the seat belts contain airbags.

[Rehaan]

Originally Posted by cool.aquarian

....
I asked a friend of mine, why Indian cars sometimes offer ABS as option, but dont offer Airbag as option.....

Simply put = COST.

Not only do they add to the cost of purchase, but for markets like india (mostly slow-speed city travelling for premium cars with the airbag option) there are a few more disadvantages :

1) They can be DANGEROUS when the person is not wearing a seatbelt or a child is sitting on the edge of the front seat or on a parents lap. Infact just earlier today i was looking at an X-Ray of a passengers leg that had been broken + ligaments torn because his foot was rested up on the dashboard during a minor 35mph collision. The airbag broke his foot, not the collision.
The awareness of airbag safety and correct use in India is close to zero. In other countries they are much more careful about it (learnt the hard way i guess).

2) One thing is the purchase cost and danger factor, but add to that the replacement cost - (very high!) everytime airbags deploy in lower-speed accidents. (They rip through parts of the dashboard etc - so that needs to be replaced too.

To put it into perspective, read this quote below :

Originally Posted by aatish

.....Airbags very vital to what it is going to cost you to set the car right. Busted airbags will add a substantial cost, so if the wreck has busted airbags that should set the valuation down by a lac at least.......

(link to thread where its from (An economical guide to rebuilding a bashed up supercar))

cya
R

[S_U_N]

Bumping an old thread. Hope this is the most appropriate one.
Just got a pre-owned Cedia. The vehicle is 4+ years old.
Does anyone know if I can check if Airbags are in good condition?
Any scanner output will show this as part of diagnostic tests?

[sukrit7]

Originally Posted by S_U_N

Bumping an old thread. Hope this is the most appropriate one.
Just got a pre-owned Cedia. The vehicle is 4+ years old.
Does anyone know if I can check if Airbags are in good condition?
Any scanner output will show this as part of diagnostic tests?

Even I would be interested in finding out if there's a check. From what I know though,the only check is the SRS light that should go off once the car is started.

[dhanushs]

Originally Posted by S_U_N

Bumping an old thread. Hope this is the most appropriate one.
Just got a pre-owned Cedia. The vehicle is 4+ years old.
Does anyone know if I can check if Airbags are in good condition?
Any scanner output will show this as part of diagnostic tests?

AFAIK, the best you can do is to check the impact sensors, and seat weight sensors, if any.

[deetjohn]

I wait for the airbags check light to go off before cranking in our cars. None of the fellas at the service center stick to this. I hate to point this out every time and they conveniently forget, every single time.

In our Swift, the light goes off if you crank the engine without waiting. But in the A-star, the light stays on for the duration even when the engine is On.

Does cranking without waiting for the light to go off cause any problems, errors etc?

[ajmat]

Airbag systems have been designed with a lot of checks and balances. If a sensor does not work, be it an impact, or a seat weight sensor or a connector, the light will show up. It is mandatory for a car to run a diagnostic check.

The only thing a diagnostic system cannot do is check the state of the chemicals inside the bag. It should last for 10 years which is the average working life of the car (in Europe and the US at least!)

Let me just add, having removed an airbag for a Skoda and replaced it back. it was the scariest repair process that I ever did. You need to disconnect the battery and leave for 30 min. Handle the unit for care and be very carefull with the wiriing harness (I've been there).

[laluks]

Originally Posted by ajmat

You need to disconnect the battery and leave for 30 min.

That is because an airbag ECU have Energy Reserve Capacitors which keep these ECUs powered for a duration (as decided by the OEM) for the ECU to wirte the crash data to the crash data recorder in the event of a crash and Battery power line is cut.

[saket77]

Please bear with my ignorance; I would like to ask some basic questions:

Once the air bags get deployed, what are the components which need change/repair? What is the approx. cost of re-instating an SRS (airbag system) once it has been deployed in case of an accident. I know, the question of cost involves a big generalization, but please answer considering its a car in the segment of say 5-10 lacs?

Also, can a person continue his journey in the same car once air bags have deployed due to a relatively minor incident & the car is otherwise fit to undertake the rest of the journey?

Thanks,
Saket

[dhanushs]

Originally Posted by saket77

Once the air bags get deployed, what are the components which need change/repair? What is the approx. cost of re-instating an SRS (airbag system) once it has been deployed in case of an accident. I know, the question of cost involves a big generalization, but please answer considering its a car in the segment of say 5-10 lacs?

Replacing Airbags is usually a very expensive affair. In most cars, the entire dashboard needs to be changed after airbag deployment. However, in some sensibly designed cars like the Figo, the dash will not get damaged, and hence cheaper replacement costs.

AFAIK, it will cost you well above 50k.

Also, can a person continue his journey in the same car once air bags have deployed due to a relatively minor incident & the car is otherwise fit to undertake the rest of the journey?

Airbags dont usually deploy in small impacts, and in case of large impacts, I'd suggest to tow to the nearest workshop. However, if driving off is so important, most cars will have a fuel cut off on impact. You might need to correct that, and then drive off.