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Discussion Starter #1
W126 Dual Airbag Retrofit Project

I just spent the last week and a half of a blissful vacation retrofitting dual airbags into my 1985 300SD. I used components pick and pulled from 1989-1991 U.S. models, to include the knee bolsters with oddments trays. I figured that since Mercedes adapted the later model W126 cars to work with dual airbags using the same platform as my earlier car by just creating new parts to facilitate the change I should be able to do the same through retrofitting these same parts myself. This is similar to the single to dual airbag retrofit project I did on my first W124 ( Passenger airbag retrofit project completed - Pics - Benzworld.org - Mercedes-Benz Discussion Forum ) ( W124 Passenger Airbag Retrofit Project Completed (with pics) - PeachParts Mercedes ShopForum ).

So for the last few years I have been gathering parts and illustrative pictures needed to complete the task. My intent has been to use only OE parts as they were used on the newer models, and I have been for the most part successful.

I did the work at my parents’ vacation place in the Adirondacks Park in upstate New York and as a consequence I had only what tools and spares I packed with me.



For the most part I brought everything I needed with me. The only exceptions to that was the need to locally purchase a hack saw blade to trim some lower portion of the dash and some contact cement to reafix two carpet pieces at the front of the rockers. Additionally, I did not anticipate that I would need to replace certain of the climate control ventilation tubing that I discovered is sized differently to fit past the knee bolster and the increased volume of the passenger airbag into the dash. Because of this I ended up reassembling the car without this ventilation tubing in place, but I will install it all once I get the parts upon subsequent pick and pull yard trips as it is available.

The project is a little more complicated than what would be appropriate for a DIY write-up. Nevertheless, I took, as many pictures as necessary to enable someone else to replicate the effort without having to take the missteps through which I had to work.

Below are a smattering of pictures of the various steps I had taken. Here is a link to the album should you want simply look through that; however, keep in mind that not all pictures are of the way I finally worked things in and there are a number of sample pictures. Also, I completed an number of other projects while I was at it (e.g. run cabling for in-trunk CD changer, evaporator drain tube, scrub carpets, better armrest, retrofit in a generation II dome light, replace cracked center brake light, replace rear window seal, etc. . .). Airbag Retrofit pictures by pwogaman - Photobucket

First I needed to completely remove all seats and carpeting for access to the cable trays (I had already removed the rear seat to make addition room for and prevent damage from my 75 pound dog). My helper.





I then needed to lay in the new wiring harness and control module. As with my W124 project, I taped the new cables with green tape. I found there was no W12 grounding point on my 85', so I tapped in with the control module mounting. The 85' module grounded in behind the instrument cluster so I also spliced that in to the grounding point I used at the control module. For the power line, I taped into the 85's line by soldering it into the newer plug.







There is an enhanced support for the steering column. First pick is the old and the new together.






The knee bolsters also serve as ventilation shafts. They pretty much bolt in.

Driver’s side:







There is an additional diagonal bar on the passenger’s side. It required drilling two holes into the center tunnel. On originally installed models there is a small plated welded to the frame. But, as I did not bring my welder with me, that will have to wait.







Aligning the dash to the bolsters was time consuming. Moving one part meant moving another, and so on. It was just tedious. As mentioned above, I needed to cut the bottom of the glove box door opening and then take about an inch off the rest of the passenger side bottom.





The seat belt buckles have sensors so they had to be replaced as well.





Things I still need to do include at least the following.
(1) install SRS label over #3 warning light socket in instrument cluster;
(2) weld passenger side diagonal bracket plate to center tunnel;
(3) acquire and install ventilation tubing;
(4) refine passenger airbag alignment;
(5) warning labels for sun visor;
(6) perform crash test - any volunteers to try the passenger side?
 

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Good work!

I just took all that crap out of my car and if I had known you were going to do this, you could have had all of my old stuff. I have everything still. Air bags, harnesses, G-sensor.
 

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Discussion Starter #3
Good work!

I just took all that crap out of my car and if I had known you were going to do this, you could have had all of my old stuff. I have everything still. Air bags, harnesses, G-sensor.
Doh! Timing is everything. Location counts for something too. What is the part number on your G-sensor?
 

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Discussion Starter #4

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Discussion Starter #6
I've gotten all the right vent tubing and I'm just waiting for warmer weather to put it in. I need to pull the dash to finish it. I also need to replace part of the center vent lever housing structure; a piece of the pot metal cracked and I'd rather replace than repair it. Any donor W126 dash will do.
 

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On a related note, by W126 has an airbag expiry, but from what I've read... they are still functional even past their expiry. What is the verdict?
 

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On a related note, by W126 has an airbag expiry, but from what I've read... they are still functional even past their expiry. What is the verdict?
yes yes i want to know this as well.

i've heard from some that the propellant can ignite too rapidly on old airbags, turning them into grenades that send the metal casings flying at you like shrapnel.

In the case of an accident, Instead of a soft gentle pillow caressing your face you get this:
 

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The Early Days of Airbags

Car airbags are part of a vehicle's supplemental restraint system (SRS). They have been around since the 1970s and are now standard equipment on every vehicle. Since airbags were new technology then, a number of automakers erred on the side of caution when estimating their lifespan. The owner's manual on early-1990s Honda and Acura vehicles, for example, recommended a dealer inspection of airbags every 10 years.

"That inspection was simply a visual inspection and a confirmation that the self-diagnostic functions were working properly," says Chris Martin, spokesman for American Honda.

Mercedes-Benz, on the other hand, was a bit more conservative. The automaker installed airbag replacement labels on all vehicles sold in the U.S. through roughly 2002, says Diedra Wylie, a spokesperson for Mercedes-Benz. The labels called for new airbags at the 15-year mark. After 2002, Mercedes research concluded that the airbags it produced after January 1, 1992 would last the life of the vehicle, Wylie says.

"Advances in airbag module technology now ensure the lifelong, functional reliability of the airbags," says Wylie.

In pre-1992 Mercedes vehicles with airbags, the part needs to be replaced after 15 years. The vehicle's owner will have to foot the bill of roughly $2,000.​


Do Car Airbags Expire?

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i've heard from some that the propellant can ignite too rapidly on old airbags, turning them into grenades that send the metal casings flying at you like shrapnel.

It's actually the opposite... as the ignitor ages and goes through more hot/cold and humid/dry cycles, it weakens. The danger being an airbag that doesn't deploy fast enough or not at all.
 

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"In pre-1992 Mercedes vehicles with airbags, the part needs to be replaced after 15 years. The vehicle's owner will have to foot the bill of roughly $2,000."

""Almost all squibs since Day One have used what is called 'glass-to-metal' sealing, which is the best for moisture protection," says Douglas Campbell, who is president of the Automotive Safety Council and has worked in the airbag industry for more than 25 years.

"Some earlier non-North American models may have used 'plastic-to-metal' seals, which would have passed the vehicle life tests, but are considered to be potentially not as robust in extreme testing," Campbell says."

OH NO! Could us w126 owners have the plastic-to-metal seals? Can someone confirm this?!
 

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2012 CL550 4MATIC Coupe
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Which is why I pulled all of mine... Everything is over 25 years old, so.....
 

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I have a couple of spare airbags, I should do a test for fun...
 

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Well yeah, that's why I did that in my coupe. I love my GB! The sedan still have the stock airbags, but in my coupe I have the AMG Momo wheel so that kills the system unless you shunt it. But I just pulled my whole system including the ballistic charges in the belts.

But, to each his/her own...
 
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But for the effort....

I do believe you should get a Do'ers award for the effort and the documentation. We should have awarded this to you when you first did it.

So here:

Welcome to the club!
 

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Discussion Starter #20 (Edited)
Mercedes issued a November 25, 2009 Service Bulletin on Airbag durability and functional reliability, SI91.60-P-0001A, that supersedes the replacement requirement for All models, providing, “German vehicle manufacturers have checked the durability and functional reliability of the airbag module and have come to the conclusion that the airbag module does not need to be changed throughout the course of the vehicle’s service life.” See below and the attached pdf file.

Save your money.


 

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