Front airbag sensor relocation?

[termite]

helping out a friend or relative who may or may not remember that old oak stump

Only two places I'm likely to touch aside from my road I know just as well as my own driveway. One if which isn't really big enough to even bother with a plow.

Too much going on this evening for me to get any time outside to work on this project. Once we get kids in bed, I'll head out to the shed and finish putting the pump together with new seals and the old pump.

 

[Erik the Awful]

Technically not supposed to tamper with, splice wiring, etc. At one time you could get pigtails to repair wiring but not sure if that's still the case as collision repair standards have changed. Nobody ever thinks it's going to happen to them, but it's not only you that you have to worry about. it usually takes frame rail damage to set off bags, bumping a curb at low speed wouldn't do it. Most switches are inertia type switches so it takes a 30-40mph to zero event to trigger. If there are injuries and the bags don't go off it will looked at hard.

I was a Nissan tech in the late '90s, not too long after airbags became standard equipment. There's a lot to unpack.

First, airbags have safeties built into them. Typically the vehicle has to be moving more than 25 mph. The first generation airbags had a centrally mounted "arming" sensor, and there were three "trigger" sensors on the bumper. The arming sensor and one of the trigger sensors had to activate at the same time for the airbag to deploy. The trigger sensors were so reliable that the second generation of airbags went to a single trigger sensor that had to activate with the arming sensor. The third generation was when they introduced seat weight sensors and discretion for when to arm the passenger airbag.

Second, we absolutely did not perform any diagnosis nor repair on airbag systems. There was a replacement tree. If the airbag light was on you started at the top of the tree and replaced parts until the airbag light went off.

Third, the sensors only sense a rapid deceleration. They do not sense crunching metal. The arming sensor and trigger sensors back then were all specifically-weighted gold-plated balls held off of two gold-plated contacts by a calibrated spring. If a wreck was hard enough, the spring would compress and the gold ball would pass current between the two contacts. It drives me f'n bonkers when I see stupid Hollywood writers use airbags as a quick gimmick to avoid them having to write real scripts. I'm looking at you, Jack Reacher! Some dude walking up and kicking your bumper is not going to set off the airbag.

During the 1st generation of airbags, Ford got sued by a family who's kid was decapitated by an airbag. Utterly horrifying and gruesome, but it was mostly the family's fault. They were driving around, looking at Christmas lights. The kid was standing in the passenger front floorboard, leaning his head on his arms over the dash. They were doing over 25 mph and got in a wreck. The airbag was right under the kid's head. Ford wasn't in the wrong, but they paid that one to keep it quiet. If Ford deserved any blame, it was for not educating customers well enough on airbags.

Alternatively, one of the guys I served with bought a GMT800 Tahoe several years ago. He always drove extremely fast and never wore a seatbelt. He was driving on the highway and looked over his shoulder for a lane change. When he looked back forward the traffic had stopped, and he slammed into the back of a car with about a 60 mph speed difference. The airbag deployed and he walked away from the crash. Without the airbag he likely would have died.

I did see a car once where a customer threatened to sue because their airbag had "suddenly deployed while driving down the road at a constant speed". A Nissan engineer was on hand when the car showed up. The service writer, technician, and engineer asked the customer multiple times, and he held true to "I was driving down the road at a constant speed." They put the car on a rack, and as soon as they lifted it they could see the front crossmember was crunched.

"I was driving down the road at a constant speed, and then I slowed down for the railroad tracks..."
"Yeah, you can pound sand."

I would rather notch the snow plow mount around the airbag sensor than move the airbag sensor. I think having an on/off switch on the airbag is a good idea, just be sure and interrupt all possible power sources. I'm no engineer, but I wouldn't want the DERM (diagnostic energy reserve module - it keeps the airbag powered if the battery cable gets severed) to be powered up and ready through some stupid sensor.

 

[termite]

I was a Nissan tech in the late '90s, not too long after airbags became standard equipment. There's a lot to unpack.

First, airbags have safeties built into them. Typically the vehicle has to be moving more than 25 mph. The first generation airbags had a centrally mounted "arming" sensor, and there were three "trigger" sensors on the bumper. The arming sensor and one of the trigger sensors had to activate at the same time for the airbag to deploy. The trigger sensors were so reliable that the second generation of airbags went to a single trigger sensor that had to activate with the arming sensor. The third generation was when they introduced seat weight sensors and discretion for when to arm the passenger airbag.

Second, we absolutely did not perform any diagnosis nor repair on airbag systems. There was a replacement tree. If the airbag light was on you started at the top of the tree and replaced parts until the airbag light went off.

Third, the sensors only sense a rapid deceleration. They do not sense crunching metal. The arming sensor and trigger sensors back then were all specifically-weighted gold-plated balls held off of two gold-plated contacts by a calibrated spring. If a wreck was hard enough, the spring would compress and the gold ball would pass current between the two contacts. It drives me f'n bonkers when I see stupid Hollywood writers use airbags as a quick gimmick to avoid them having to write real scripts. I'm looking at you, Jack Reacher! Some dude walking up and kicking your bumper is not going to set off the airbag.

During the 1st generation of airbags, Ford got sued by a family who's kid was decapitated by an airbag. Utterly horrifying and gruesome, but it was mostly the family's fault. They were driving around, looking at Christmas lights. The kid was standing in the passenger front floorboard, leaning his head on his arms over the dash. They were doing over 25 mph and got in a wreck. The airbag was right under the kid's head. Ford wasn't in the wrong, but they paid that one to keep it quiet. If Ford deserved any blame, it was for not educating customers well enough on airbags.

Alternatively, one of the guys I served with bought a GMT800 Tahoe several years ago. He always drove extremely fast and never wore a seatbelt. He was driving on the highway and looked over his shoulder for a lane change. When he looked back forward the traffic had stopped, and he slammed into the back of a car with about a 60 mph speed difference. The airbag deployed and he walked away from the crash. Without the airbag he likely would have died.

I did see a car once where a customer threatened to sue because their airbag had "suddenly deployed while driving down the road at a constant speed". A Nissan engineer was on hand when the car showed up. The service writer, technician, and engineer asked the customer multiple times, and he held true to "I was driving down the road at a constant speed." They put the car on a rack, and as soon as they lifted it they could see the front crossmember was crunched.

"I was driving down the road at a constant speed, and then I slowed down for the railroad tracks..."
"Yeah, you can pound sand."

I would rather notch the snow plow mount around the airbag sensor than move the airbag sensor. I think having an on/off switch on the airbag is a good idea, just be sure and interrupt all possible power sources. I'm no engineer, but I wouldn't want the DERM (diagnostic energy reserve module - it keeps the airbag powered if the battery cable gets severed) to be powered up and ready through some stupid sensor.

I enjoy the background and knowledge everyone on this forum shares freely. Thank you Erik and everyone else.

Getting it all mounted up is the plan for this afternoon. Slow day at work so should be home with daylight to spare and no kids underfoot. Will update tonight on my approach.

 

[Hipster]

I was a Nissan tech in the late '90s, not too long after airbags became standard equipment. There's a lot to unpack.

First, airbags have safeties built into them. Typically the vehicle has to be moving more than 25 mph. The first generation airbags had a centrally mounted "arming" sensor, and there were three "trigger" sensors on the bumper. The arming sensor and one of the trigger sensors had to activate at the same time for the airbag to deploy. The trigger sensors were so reliable that the second generation of airbags went to a single trigger sensor that had to activate with the arming sensor. The third generation was when they introduced seat weight sensors and discretion for when to arm the passenger airbag.

Second, we absolutely did not perform any diagnosis nor repair on airbag systems. There was a replacement tree. If the airbag light was on you started at the top of the tree and replaced parts until the airbag light went off.

Third, the sensors only sense a rapid deceleration. They do not sense crunching metal. The arming sensor and trigger sensors back then were all specifically-weighted gold-plated balls held off of two gold-plated contacts by a calibrated spring. If a wreck was hard enough, the spring would compress and the gold ball would pass current between the two contacts. It drives me f'n bonkers when I see stupid Hollywood writers use airbags as a quick gimmick to avoid them having to write real scripts. I'm looking at you, Jack Reacher! Some dude walking up and kicking your bumper is not going to set off the airbag.

During the 1st generation of airbags, Ford got sued by a family who's kid was decapitated by an airbag. Utterly horrifying and gruesome, but it was mostly the family's fault. They were driving around, looking at Christmas lights. The kid was standing in the passenger front floorboard, leaning his head on his arms over the dash. They were doing over 25 mph and got in a wreck. The airbag was right under the kid's head. Ford wasn't in the wrong, but they paid that one to keep it quiet. If Ford deserved any blame, it was for not educating customers well enough on airbags.

Alternatively, one of the guys I served with bought a GMT800 Tahoe several years ago. He always drove extremely fast and never wore a seatbelt. He was driving on the highway and looked over his shoulder for a lane change. When he looked back forward the traffic had stopped, and he slammed into the back of a car with about a 60 mph speed difference. The airbag deployed and he walked away from the crash. Without the airbag he likely would have died.

I did see a car once where a customer threatened to sue because their airbag had "suddenly deployed while driving down the road at a constant speed". A Nissan engineer was on hand when the car showed up. The service writer, technician, and engineer asked the customer multiple times, and he held true to "I was driving down the road at a constant speed." They put the car on a rack, and as soon as they lifted it they could see the front crossmember was crunched.

"I was driving down the road at a constant speed, and then I slowed down for the railroad tracks..."
"Yeah, you can pound sand."

I would rather notch the snow plow mount around the airbag sensor than move the airbag sensor. I think having an on/off switch on the airbag is a good idea, just be sure and interrupt all possible power sources. I'm no engineer, but I wouldn't want the DERM (diagnostic energy reserve module - it keeps the airbag powered if the battery cable gets severed) to be powered up and ready through some stupid sensor.

I saw that Reacher episode. lol I've seen all kinds of bs claims made by customers in the collision biz. "the bags inadvertently went off....then I hit the guardrail." Uh, huh, insurance adjusters don't buy it either. Happens more often than not and it's not a system to be hackered with splices, butt connectors, etc. because you can make the bags deploy, early, late, or not at all. They are placed is specific locations for a reason. a deceleration switch is still an inertia switch. Didn't really feel the need to get into gold contacts and rocket fuel as deployment methods.

 

[Scooterwrench]

I've heard that a very small charge of C4 is what is used to blow them out.

 

[Hipster]

I've heard that a very small charge of C4 is what is used to blow them out.

In I-Car trining was explained to me a rocket fuel, but that was quite a few years ago as well. The bags seem similar to woven fire blanket material...not all that different than a treated fiberglass welding blanket. In the early days of bags people reported burns. Now the complaint is abrasions. I've had to re-cert along the way but the one thing that remained constant is not to tamper with, hack, or modify the srs systems. The deep down technicals, to me, aren't really all that relevant. Contrary to what Erik believes the rate of collapse has a definite effect on the inertia switch. It's not debatable. Lighter weight impact bars,bumper face bars, prior or unfixed frame damage etc. can all have an effect on airbag timing. If stuff collapses too fast or your repair too stiff it alters air bag timing. There are guidelines and training for all of it that surpasses things covered in Oem collision repair guides.

 

[termite]

So, finally able to make some headway this evening/night. The mount is nearly installed with exception of the one bace that interferes with the airbag sensor.

Only half decent place I can think of for attaching it and not tampering with air bag is the bracket for the sway bar. Mock up is below. What say you folks on that attachment point?

You must be registered for see images attach

 

[Hipster]

So, finally able to make some headway this evening/night. The mount is nearly installed with exception of the one bace that interferes with the airbag sensor.

Only half decent place I can think of for attaching it and not tampering with air bag is the bracket for the sway bar. Mock up is below. What say you folks on that attachment point?

You must be registered for see images attach

Doesn't look like you messed with the sensor, but it's "extreme" close up on my end. Kind of not enough to see what's going on. Kind of rather hear " I trimmed/modified a bracket so I could bolt it on here" Not 100% sure what's going on but not tampering with the sensor is the better option.

 

[termite]

Doesn't look like you messed with the sensor, but it's "extreme" close up on my end. Kind of not enough to see what's going on. Kind of rather hear " I trimmed/modified a bracket so I could bolt it on here" Not 100% sure what's going on but not tampering with the sensor is the better option.

Its just clamped on temporary for now and its sagged a hair. If I drill and secure it to the sway bar bracket, it'll be about an inch below the sensor, and have about 3/8 clearance above the sway bar. Would be tight to the lower frame section. Will also require shortening the brace and redrilling the opposite end.

 

[Erik the Awful]

I've heard that a very small charge of C4 is what is used to blow them out.

It is an explosive charge, but a quick google search says that C4 is hexahydro-1,3,5-trinitro-1,3,5-triazinem while early airbags used sodium azide, and modern airbags use guanidiniam nitrate. The selling point of C4 is that it's completely inert until you subject it to a specific condition. You can burn C4 and it doesn't explode. You can get it wet and it doesn't change the explosive power. I'd guess it probably also has a pretty decent shelf life.

Sodum azide and guanidinium nitrate are similar that they stay inert until subjected to a specific condition. They're not hygroscopic, so they won't soak up moisture and change their properties.

Which brings up Takata airbags. Takata was getting killed by competitors in the airbag market. Instead of hiring more or better engineers to make their product better, they tried to make their product cheaper. Sodium azide isn't inexpensive, but ammonium nitrate is. The problem is that ammonium nitrate is very hygroscopic, and when it absorbs water it becomes both more powerful and shock-sensitive. Management demanded that the engineers find a way to make ammonium nitrate usable. When engineers explained that it was unsafe and unworkable they were fired. The engineers that tried to work a solution basically just tried to seal the ammonium nitrate as best they could. But when you're dealing with millions of airbags, some of the seals aren't going to work so well. In Japan, cars are completely dismantled in salvage yards, and several salvage yard workers got killed by Takata airbags before the investigations started. Here in the states, there were several gulf coast accidents where the airbags went off far too violently - including one accident where a Takata airbag sent shrapnel though the neck of a young woman, killing her. When the NHTSA and Japanese authorities started investigating, they found the seals were failing and the airbags were dangerously powerful and extra-sensitive. They were responsible for at least 11 deaths and 180 injuries. Takata got handed a $1 billion fine and three executives were indicted.

As an aside, ammonium nitrate is the explosive that Timothy McVeigh and Terry Nichols used to blow up the Murrah Building here in Oklahoma City in 1995.

Here's a pretty good reference.

What chemicals make airbags inflate, and how have they changed over time?

cen.acs.org

Contrary to what Erik believes the rate of collapse has a definite effect on the inertia switch.

Don't go putting words in my mouth. That's not what I said.