Uh-oh...will this make my seat air bags go off??
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Thread: Uh-oh...will this make my seat air bags go off??

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    Default Uh-oh...will this make my seat air bags go off??

    As some of you know, I have swapped the leather seats from my 2001 written-off Scenic to my "new" 2003 Scenic.
    Each seat has 1 black, 2 brown and 2 blue wires, and each car has the same. But of course the plugs are different between the cars!!! It seems there is a short between each of the blue/brown pairs, so each pair actually goes to the same place(?) and I'm guessing that's a safety redundancy?
    But what if I join a blue/brown pair in the seat to the wrong blue/brown pair in the car? Will the air bags go off? Is there even a wrong blue/brown pair?
    There seems to be a faint 2mm green line on one of the pairs, but I'm not willing to bet my seats on it, so I'm hoping somebody here knows the answer please?

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    1000+ Posts jo proffi's Avatar
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    I don't know the answers to your airbag questions, but for our sadistic amusement, can you please make sure you have a video camera rolling for when you wire them up.

    Jo

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    1000+ Posts FIVEDOOR's Avatar
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    Lesson on how airbags work

    https://www.youtube.com/watch?v=KcScD2tlgK0
    Any day I wake up and don't have to go to work, is a good day
    Every day is a good day

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    Very funny guys!

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    1000+ Posts robmac's Avatar
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    the additional pair "with a short" is more than likely a form of safety device to signal to the Body module that airbags are not unplugged and thus ineffective.

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    Thanks mate, but I didn't explain it well enough. BOTH blue/brown pairs are shorted.
    i.e. a brown wire and a blue wire enter the each plug from the back, but then a small metal fitting within each plug shorts the blue and brown together. Removing the small metal fitting and testing the resistance between the ends of the blue and brown wire also show that they are shorted somewhere else. So it's as if they are running the two wires separately but they do the job of one wire. This is true for each of the two plugs

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    1000+ Posts Haakon's Avatar
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    Yeah, I bet those plugs are there to stop the body computer from flipping out about the airbags being absent.

    Odd way to do it, I'd have assumed they were simply deleted in the ECU's software and you'd have to plug the computer into a diagnostic computer to enable the airbags? Or is the scenic 1 a bit old school fo rthat?

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    Quote Originally Posted by goog64 View Post
    Thanks mate, but I didn't explain it well enough. BOTH blue/brown pairs are shorted.
    i.e. a brown wire and a blue wire enter the each plug from the back, but then a small metal fitting within each plug shorts the blue and brown together. Removing the small metal fitting and testing the resistance between the ends of the blue and brown wire also show that they are shorted somewhere else. So it's as if they are running the two wires separately but they do the job of one wire. This is true for each of the two plugs
    Failsafe duplicated wiring perhaps, on an airbag that can only be a good thing. It's unlikely to be for increased current carrying capacity I would have thought.

    By the nature of the wiring it can also detect if the plug is disconnected.

    The designer could be ex Dassault airccraft engineer.

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    Quote Originally Posted by goog64 View Post
    Thanks mate, but I didn't explain it well enough. BOTH blue/brown pairs are shorted.
    i.e. a brown wire and a blue wire enter the each plug from the back, but then a small metal fitting within each plug shorts the blue and brown together. Removing the small metal fitting and testing the resistance between the ends of the blue and brown wire also show that they are shorted somewhere else. So it's as if they are running the two wires separately but they do the job of one wire. This is true for each of the two plugs
    Good grief. No doubt there is an explanation in the evolution of the model over time. You could try writing it in French. It will make no less sense....
    JohnW

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    Well guys, Jaahn just paid me a visit (and again it was invaluable). He discovered that the small metal fitting that shorts the two wires together is actually pushed out of the way when the plugs are joined. So it is only there to short the wires when the air bag is unplugged (Jaahn thinks this might be to stop a stray charge from setting off the air bag).
    And I made a mistake - with that metal piece removed the wires are NOT still shorted - they actually read 3 ohms (which from my understanding is the correct air bag resistance).
    Anyway, I am going to put my faith in the little green and white tracers painted faintly on the wires and go outside and figure out what connects to what.

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    1000+ Posts robmac's Avatar
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    You can always test your wiring later to confirm every thing OK.

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    As I found with my 406 door locking issue, all the wires should have numeric codes, written vertically along the wire (if they are using the same system as PSA).

    I have found that the colours are not maintained on either side of a connector plug, but the numbers will be the same (of course when swapping parts this is only true if the cars are the same model, and very similar in age).

    Cheers

    Alec

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    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by Armidillo View Post
    (if they are using the same system as PSA).
    I bloody well hope not!!!

    Jo

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    Veni Vidi Posti 68 404's Avatar
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    It's a Renault. Of course the airbag light will be permanently on!

    Dave
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    Quote Originally Posted by Armidillo View Post
    As I found with my 406 door locking issue, all the wires should have numeric codes, written vertically along the wire (if they are using the same system as PSA).

    I have found that the colours are not maintained on either side of a connector plug, but the numbers will be the same (of course when swapping parts this is only true if the cars are the same model, and very similar in age).

    Cheers

    Alec
    Thanks Alec. My eyes aren't the best, but I can't see any numbers. I will find out tomorrow if I've made a mistake.

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    Default Air bag wires !!

    Hi
    A couple of general comments on the wires as I observed them.

    Firstly a safety warning There are warning against probing the airbag wires under any circumstances with any device, like a multimeter, which puts out a voltage which COULD trigger them. You have been warned.

    Both the female plug and the male plug under the seat had devices fitted into the half connectors which shorted the pins together when disconnected. When the plug was pushed together the metal shorts would be pushed out of connection with the pins. Just for your information.

    The change of plug wiring was this; The seperate two airbag plugs and the third seat heater plug had been replaced by a large multi plug which had them all in one. However the wires appeared to be the same colour codes. No numbers on them, basic colour with a broken dash tracer. Faint Wiring colours maintained across the plug !

    Jaahn
    Last edited by jaahn; 25th October 2015 at 11:36 AM.

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    Hi Jaahn,
    Thanks mate. As you know, I did put my multimeter across that air bag plug, with the short removed. I'm so glad it didn't go off.
    I painstakingly checked and cross-checked and figured out which wires in the old seats connected to which wires in the old car (I used your stick-a-pin-in-the-wire method to determine which plug pins belonged to which wire (it was always opposite to how it looked).
    Fortunately, even though the plugs differ, both cars have the same coloured wires coming out of them, so I made the big assumption that the new car would join up the same way as the old.
    I have now joined and soldered (if you could call it "soldering" - I am still completely hopeless at that) and heat shrunk all the connections on both seats. I turned the ignition on, nothing blew up and the SERV and air bag warning lights are out. Yay!
    Interestingly both seats have a brown to brown, blue to blue and two brown to blue connections.

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