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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > Can an airbag go off with no power?



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      09-06-2011, 04:18 AM   #1
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Can an airbag go off with no power?

Quick question - hopefully,

I have a trim replacement to do on my wheel - if the battery is fully disconnected from the car - can the airbag still be activated at all?
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      09-06-2011, 04:24 AM   #2
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From memory the airbag has to always be treated with great care. Even when removed from the car it can exploded if dropped etc.

If you are removing the trim around the wheel its possibel to do it without removing the airbag found a DIY a while back.

Otherwise I recall reading you want to disconnect battery for good 30 min to 1 hour before starting removal procedure on the air bag. I would then ensure you wear good high strength eye protection and take great care not to apply any heavy hits, knocks to the unit while removing and once removed. Treat it like a loaded grenade since it pretty much is.
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      09-06-2011, 04:33 AM   #3
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No.

The 'detonation' is electically operated.
And is actually a rapid gas release from a chemical reaction.

You cant have airbags tripping by accident in a vehical for obvious reasons, so they are quite robust and foolproof.
Why not just unplug the modular connector, ignition OFF, to the assembly for simplicity?

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      09-06-2011, 04:41 AM   #4
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Thats true but if you drop it they can go off hence all the warnings, especially as they have and hold charge for a while after battery is removed.
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      09-06-2011, 04:44 AM   #5
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What I want to know then is whether they need a potential (voltage) to activate or just a contact then I guess.

Re doing trim without wheel/airbag off - mine may be different - 6 series.
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      09-06-2011, 04:46 AM   #6
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Some advice I found elsewhere:-

Warning: The install requires removal of the Airbag.

1. Turn the steering wheel so the bottom spoke is on top.
2. On the M6, lower the windows (once the battery is disconnected, the window makes the door hard to open)
3. Disconnect the negative terminal of the battery (wait half an hour, just in case) -- This is for Airbag safety
4. Push a screwdriver into the hole in the back of the steering wheel. There is not a screw, just push against a "spring" and the airbag will be fall forward -- leave the wires attached.
5. Remove 2 T-20 torx screws, and gently pull the trim (including the buttons) from the wheel
6. Remove 4 T-20 torx screws, that attach the trim and the pods with the buttons.

Installation is the reverse, with these notes.
1. The airbag held in place with 4 spring loaded hooks, and with snap in place without tools.
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      09-06-2011, 04:51 AM   #7
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I've never heard of an airbag going off from being dropped as it's an electrical trigger to a capacitive detonator - it's not nitroglycerin.

They have to be robust enough to be handled during manufacture and transportation to the car factories so whilst not impossible I'd be amazed if you could set one of by dropping it.
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      09-06-2011, 05:13 AM   #8
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I'm sure it would take a lot to make it go off but then with anything like that better safe then sorry. I've removed my airbag few times on e46 when I did some trim work and the warning messages said it all. With anything like that better safe then sorry especially as it could even be reveres dropping it could make it fail and not work.
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      09-06-2011, 05:19 AM   #9
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Absolutely, I fully agree with your "better safe than sorry" because it is potentially dangerous, not to mention the fact that you might damage it, and disconnecting the battery is essential, but you'd have to give it a good hiding to trigger it simply by impact.
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      09-06-2011, 07:25 AM   #10
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Having handled explosives and detonators before please be aware of how susceptable they are to static electricity. I wouldn't risk walking over a cheap nylon carpet and then touching the pins once removed!
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      09-06-2011, 07:36 AM   #11
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Quote:
Originally Posted by CraigUK View Post
Having handled explosives and detonators before please be aware of how susceptable they are to static electricity. I wouldn't risk walking over a cheap nylon carpet and then touching the pins once removed!


They certainly go with a bang.....check out this clown!

Last edited by M3-FAST; 09-06-2011 at 10:56 AM..
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      09-06-2011, 08:01 AM   #12
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Brilliant .

Paul, make sure you set up the video before you start, You've Been Framed might be interested in the results .
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      09-07-2011, 05:32 AM   #13
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No videos Rog!! - battery disconnected - I'll give it 20 mins then see what happens.
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      09-07-2011, 05:51 AM   #14
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Just to point out, different style steering wheels have different methods of airbag retention!

Whilst all based on spring clips they are in different locations on SE wheels and MSport wheels.

I fiddled about for ages trying to get my SE wheel's airbag off only to find, after extensive web searching, that it was different from the MSport wheel I intended to fit and had in my hand, so to speak.

The SE wheel spring clips are vertically up from the release access hole and require swinging the clip to the side and inwards whereas MSport wheel is a straight push in horizontally.

You live and learn!
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      09-07-2011, 06:34 AM   #15
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Mine was a straight push down and off. All done - interior looks much better now.
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