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Old 12-17-2002, 02:36 PM
hedpe's Avatar
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Join Date: Oct 2001
Posts: 507
why didn't my airbags go off in my 500E?

Hey guys, trying to keep a long story short. I was in a one car accident in my 1992 500E. Someone pulled out in front of me when i was reading one of those "BUCKLE UP DRIVE SAFE" flashing signs, when i looked forward i noticed i was practically kissing his back bumper, had to swurve to miss him. Heres the important part:

The left side of my car hit the left barrier doing about...45 maybe? Then i bounced off the left barrier and it threw me across the road and smacked me into the right barrier probably at about 40mph, it really sent me flying for some reason. When i hit the left barrier i hit it basically exactly at my side, it smashed my two left wheels, and scraped my front bumper on the side, and my lower side panels.

When i hit the right barrier, i was basically sideways, and my rear end smashed in to it, my right rear end corner. The body was barely damaged, but my lower bumper was coming off and bent up like an accordian. So basically, the impact was at my back bumper, right side.

After hitting that, i was thrown into the middle of the road. and my airbag never went off?

Was it a faulty airbag or do they only go off front impact? Past a certain speed? What's the deal?

The car should be ok, i'm actually pretty proud at how well it held up. The hard shell of the car basically only suffer a couple scrapes it looked like, but the flimsy bumpers took all the damage. I'm pretty impressed with how the car held up. Atleast I know they're built like tanks now

I was countersteering pretty hard to not hit the sides all that hard, which helped in the slightest, because if i would have had about 10 more feet before that right barrier i wouldn't have hit it.

But it all happened so fast, i'm just glad i'm ok. Cars are shoulder thats killing me isn't I wish I could take it to an autobody shop

But why didn't my airbags go off? Anyone?

2013 C300 4matic
2009 C300 4matic

2001 E320 Sport
1992 500E
1989 300SEL
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Old 12-17-2002, 02:49 PM
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Join Date: Apr 2002
Location: Melbourne, Australia
Posts: 280
Talking airbags

I thought the front airbags require a certain degree of almost direct frontal damage before they blow up. The sensors should be located somewhere behind the front bumper area on the chassis. The same should apply for the side airbags which only just came into fashion a few years ago. Rear impacts should not trigger the front airbags as they are meant to protect from frontal knocks and protect the driver and front passenger from smashing their faces into the dash and windscreen. This is only a layman's opinion by the way, thank goodness you walked away without any major injury! That is why we drive the Benzs, they are built like tanks!
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Old 12-17-2002, 03:14 PM
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Join Date: Aug 2001
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Posts: 3,044
From your description of the incident, you should be glad they didn't deploy!! If they had, you would have been blinded and lost any control of the situation after the inital hit.
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Old 12-17-2002, 03:14 PM
MikeTangas's Avatar
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Join Date: Apr 2000
Location: So. Cal
Posts: 4,430
Obviously your crumble zones crumpled properly and absorbed most of the energy of impact. The impact energy needs to be sensed by the SRS control module mounted on the tranny hump before the bag(s) deploy.

While I'm thinking about it, check to see if your seat belts freely retract now after the impact. If not, the module sensed enough of the impact to deploy the ETR (seat belt retractors). If they don't freely retract when you pull them out, the seat belt units will have to be replaced.
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

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Old 12-17-2002, 03:27 PM
I told you so!
Join Date: Jun 2002
Location: Motor City, MI
Posts: 2,852
Hocky is right, the sensors only measure the forward decelleration for front airbag deployment. Manufacturers try to make sure air bags go off only when they're needed... a rather daunting task. From what you described, most of the force was sideways in your episode. Your car's safety equipment performed as it should have.

BTW, lateral head injuries are more lethal than frontal head injuries - hence, the safety push for side curtain air bags. Consider yourself lucky.
95 E320 Cabriolet, 159K
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Old 12-17-2002, 03:32 PM
MikeTangas's Avatar
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Join Date: Apr 2000
Location: So. Cal
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OK, read that backwards, thought he'd hit head on, then slid sideways to the other side. That's what I get for trying to quick read while at work. Side impacts should not deploy the bags aither (unless equipped with side curtains I think).

Agree that the sensor only reads frontal deceleration, normally wont deploy from a rear end impact.
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon least its a diesel

Non illegitemae carborundum.
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Old 12-17-2002, 04:11 PM
blackmercedes's Avatar
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Join Date: Dec 2000
Location: St. Albert, Alberta, Canada
Posts: 3,492
Unlike most makers, Mercedes sees airbags as the final 10% required for severe impacts.

They engineer their airbags to deploy in certain situations:

1. A very high threshold if your seatbelt is buckled. If you're unbelted (Attention Yanks...) then the threshold is reduced.

2. Occupany sensors (in later cars) mean that passenger bags don't deploy if the seat is unoccupied. Saves bucks.

3. Side impacts do not deploy front amounted air bags. Side impacts deploy side/curtain bags when so equipped. Front mounted bags do not deploy in rear-end collisions unless the secondary collision is intense enough to cause forward decelleration high enough to trigger the bag.

The car uses an accelerometer in the passenger compartment and impact sensors in the front of the car. In case of electrical failure, the voltage required to activate the trigger is VERY low.

Mercedes is one of only two manufacturers on record as not having faulty (non-deploying) or unintended deployments. The other is BMW. MB's bags are regarded as the best and most reliable on any car sold. Kinda figures since they were the first to install them...
John Shellenberg
1998 C230 "Black Betty" 240K
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Old 12-17-2002, 04:56 PM
Michael's Avatar
Join Date: Jul 1999
Location: Boston, USA
Posts: 2,700
The bags only blow upon frontal impact within (as I recall) 13 degrees of straight-on. Why blow a bag when it won't help you but WILL blind you? Unlike my neighbor's Toyota tercel; his car rolled across the street and hit my house ever-so-slightly (virtually no damage to the house) because his parking brake wasn't properly set...since both bags blew upon the crushing of some cheap sensors in the bumper, his car ended up a total loss!! (passenger-side bag required replacement of entire dash for something like $5k US)

The only sensor is an accelerometer, and it is just forward of your shift lever.

Glad you're okay! And get therapy ASAP on that shoulder so you minimize/eliminate any permanent impairment

"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

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