The air bags don't go off in my case. I totaled my car with a head on collision and I they didn't go off. I suppose I was going under 10mph :laugh:
The way air-bags work, in general, is that an array of sensors (including acceleration/shock sensors, and possibly gyroscope/spin rate sensors) feed into a computer control unit. Using the data, the computer determines the pattern of impact, and using a set of rules determines whether the air-bag(s) should deploy.
The air-bags are operated by electrically detonated explosive charges, which produce a controlled burst of high pressure gas to inflate the bags - similar explosive charges may be used to increase the tension in seat-belts during impact (seat belt pre-tensioners).
The air bag control unit may be powered even when the car is off, and probably usually is. But I suppose, it may vary between manufacturers.
There are several concerns over maintaining or servicing air-bag equipment. Any unintended short circuit (e.g. cable damaged, incorrect connection, slipped multimeter probe) in the air-bag circuit could potentially energize the detonator - because of this, the recommendation is that no maintenance be carried out on an air-bag system unless the battery is disconnected and/or removed from the vehicle. Even then, there are strict maintenance procedures to be followed, as there is a theoretical risk that static electricity, or test currents from a multi-meter probe, could trigger detonation.
The air-bags are operated by electrically detonated explosive charges, which produce a controlled burst of high pressure gas to inflate the bags - similar explosive charges may be used to increase the tension in seat-belts during impact (seat belt pre-tensioners).
The air bag control unit may be powered even when the car is off, and probably usually is. But I suppose, it may vary between manufacturers.
There are several concerns over maintaining or servicing air-bag equipment. Any unintended short circuit (e.g. cable damaged, incorrect connection, slipped multimeter probe) in the air-bag circuit could potentially energize the detonator - because of this, the recommendation is that no maintenance be carried out on an air-bag system unless the battery is disconnected and/or removed from the vehicle. Even then, there are strict maintenance procedures to be followed, as there is a theoretical risk that static electricity, or test currents from a multi-meter probe, could trigger detonation.
Modelworks
Lifer
- Feb 22, 2007
- 16,240
- 7
- 76
Something interesting about airbags.
If you look at auto salvage sites you can see lots of pictures of cars where the airbags never deployed.
These weren't small crashes either. Some cars rolled over, had the entire front smashed or the sides and backs smashed.
I just shake my head in disbelief.
If you look at auto salvage sites you can see lots of pictures of cars where the airbags never deployed.
These weren't small crashes either. Some cars rolled over, had the entire front smashed or the sides and backs smashed.
I just shake my head in disbelief.
People making a lot of assumptions here. Note, with the car in the off position, the clock still functions. If it's a digial clock, it functions too, even though you can't see it. So the notion that if the car is off, therefore that air bags are off is empty. The one does not imply the other. The determiner here is not whether the key is on or off, but whether the airbag is wired into the ingnition switch, or if get's it's power directly from the battery. Let's try not to come to conclusions using bad logic. H
Anyways, to answer the question, the airbags are wired thru the ignition switch, so they should not function when the key is in the off position. I say should, because if someone rams into you car, the chance of an electrical short is there, so while very unlikely, there remains the posibility.
Edit, I see some have sited info that suggests at least some cars wire the air bags directly to the battery.
Anyways, to answer the question, the airbags are wired thru the ignition switch, so they should not function when the key is in the off position. I say should, because if someone rams into you car, the chance of an electrical short is there, so while very unlikely, there remains the posibility.
Edit, I see some have sited info that suggests at least some cars wire the air bags directly to the battery.
Mermaidman
Diamond Member
- Sep 4, 2003
- 7,987
- 93
- 91
My car's factory manuals say to disable the airbag system prior to working on steering wheel stuff. (Oldsmobile)
Two main reasons you disconnect the battery when you work on a car:
1 - safety, don't want to hurt yourself. Much safer if there is no power
2 - to avoid accidentally setting off the airbags.
1 - safety, don't want to hurt yourself. Much safer if there is no power
2 - to avoid accidentally setting off the airbags.
Zenmervolt
Elite member
- Oct 22, 2000
- 24,512
- 21
- 81
Yes, if you're working on the steering column it's possible to touch off the explosives used to activate the airbag. But if the car is just sitting there with the ignition off the sensors should not be active.
At least on my Volvo, with the key off, the little computer that controls the airbags does not have power until the key is in the "run" position. Note that the key being in the "run" position is not necessarily indicative of the engine running. The computer cannot trigger the airbags if the car is turned off since it doesn't have power. The airbag circuits may or may not be continuously energized, but the signaling computer is not.
The assumption was that the OP was talking about a car that was parked with the keys out of the ignition.
ZV
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