vert

I posted this question in another thread, but I doubt the right people will see it. I need to take out the airbag connectors and connect the wires without the connectors which are causing an SRS problem as described in the last post on this page: https://mbworld.org/forums/c-class-w...ng-dealer.html

I need to order butt splice connectors, the ones that you heat up and the solder ring melts fusing the wires together and heat shrinking for a weatherproof seal. I need to know the gauge of the connector to order which of course is based on the wires for the airbag in the door panel. Anyone knows?

LILBENZ230

You are going to kill yourself trying to save a few dollars. Modifying the SRS system is not something you should consider, kind of like Russian Roulette.

vert

I am not modifying the SRS system, I am following a Mercedes bulletin posted in my other thread. It is the same thing that a dealer will do, there is only one way of doing it and other people have done it. I also have the computer to reset the light after it's finished.

torake

I just hand-spliced them and put two pieces of heat shrink tubing on there.
Maybe you can figure out the gauge from the picture?



My error codes were "ignition circuit, high resistance". Went away with this fix as per the bulletin (and a code reset).
Good luck

Moviela

The wire size is closest to AWG 18. The problem seems to be tin connectors in the door sill that fret from micro-motions of the pins. In many circuits it would make scant difference to the operation of the device. In the case of the airbag squids the measurement is done with a very low current test. Some people call this a dry circuit, and it will not work with any high impedance across the connector.

Mercedes solution is to cut out the connector and use a heat activated butt splice to complete the circuit. I find the splice to be a source of further trouble. Those splices require about 700 degrees F to melt the solder and properly wet the wire and terminal to form a gas tight seal. When you are done it is impossible to inspect the quality of the solder joint because it is covered by the shrink wrap. The heat gun to do that is very expensive, and that much hot air can cinge nearby paint, plastics, and carpet. (Don't ask me how I know this, or why my friend's C300 is sporting a new front carpet.)

Crimping is the best way to make a butt splice in the automotive enviornment. A certified crimp will eliminate gas from the connection, will have a higher mechanical bond, and will not corrode like solder. It also does not need the flux to be removed as soldering does. In a wet location like under the hood, you can use heat shrink tubing with integrated sealant over the butt splice. This will keep it drier than the North end of a Southbound duck on the lake.

You can also consider changing the connector to an TYCO/AMP or Molex connector housing that uses .090" diameter gold pins. This makes it possible to separate the circuit in the future for testing.

torake

I inspected the connectors on removal, and from the looks of the pins, they were indeed gold plated.
Couldn't see anything wrong with it, and once i touched it to remove it from the vehicle, the extra resistance it added was gone.

According to the bulletin, MB demanded that faulty connectors be sent in to their technical department for inspection, but that's not the case an more.

The main usefulness of the connector is for replacing the door or the door harness. Soldering it as we do require cutting and re-soldering should you ever need to.

vert

Thank you SO much for posting your successful DIY. Could you tell me more about the exact method that you used to connect the wires back together after cutting out the MB connector? Did you twist the wires together, then solder, then heat-shrinked without any butt splices at all?

Also, did you do all 4 doors or just the door that was giving the error? For example, my SRS code indicates that the problem is on the front driver side airbag. Should I cut out just that one connector, or do I need to do it on all 4 doors as MB bulletin says?

Any other tips? How long has it been since you fixed this without the SRS light coming back after you reset it?

It looks like you have 2 wires done in that picture, while the bulletin talks about 3 wires per bag?

Also, did you disconnect the battery or just did this while the key was out of the ignition. Bulletin does not say to disconnect the battery.

torake

• Keys out and away from vehicle
• Find yellow connectors in door sills and cut them out
• Prepare shrink tubing on all wires.
• Splice wires by twist and solder, then inspect for solder penetration
• Heat the shrink tubing
• Reassemble door sill
• Check and reset using Star

I did both back doors 6 months ago, 10.000 kms w/o problems since then.

vert

It sounds like I can try to fix just the door that is giving the error - front driver side, instead of doing all 4. Good to know that the battery did not have to be disconnected.

I am going to try doing exactly what you did - cut out the connector, twist and solder the wires together instead of looking for those hi-temp butt splices.

vert

OK, before I cut into the wiring - the yellow connector with two wires (see picture) is the one I am replacing with a direct solder connection, correct? I don't see any other yellow connectors under there, so this must be right, but figured I'd ask one more time!

torake

That looks like the one, but I don't have the wiring diagram available so I can not double check the cable colors for you atm.
If you want to make 100% sure, take off the door card and check the wire colors on the bag.
... or just do it. The worst that'll happen is that you'll have to re-open the sill and dig for another yellow connector if the error does not clear.

vert

That's the route I took I reset the SRS light and now need to wait to see if it stays off. Prior to the fix and just with a reset, the light came back within a week or so and hopefully after cutting out that yellow connector it will stay off.