Seat Belt Tensioner Wiring Question

[ANUSTART]

Does it matter what order the two wires are in when putting them back in the yellow wiring harness plug? I tried to keep track of the two and one of the pieces of tape I used to mark, came off. Thanks!

[Shipkiller]

Looking at the schematic, it matters.

Since you did not specify which side, I will start on the left:

From the left b-piller satellite, the two wires leave on pins 14 and 15.
Pin 14 goes to the X275 connector (yellow one underseat) on pin nine (9) and it is RED (RT). Pin nine outputs to pin 2 on seat belt tensioner.
Pin 15 goes to the X275 connector on pin 10 Blue/Brown (BL/BR). Pin 10 outputs to pin one (1) on the seat belt tensioner.

This is the same for the right side.

[ANUSTART]

Originally Posted by Shipkiller

Looking at the schematic, it matters.

Since you did not specify which side, I will start on the left:

From the left b-piller satellite, the two wires leave on pins 14 and 15.
Pin 14 goes to the X275 connector (yellow one underseat) on pin nine (9) and it is RED (RT). Pin nine outputs to pin 2 on seat belt tensioner.
Pin 15 goes to the X275 connector on pin 10 Blue/Brown (BL/BR). Pin 10 outputs to pin one (1) on the seat belt tensioner.

This is the same for the right side.

Thanks for the info. I'm unsure how to proceed as both of my wires coming off of the seat belt tensioner are black. No other identifiers are present. I checked upstream from the pin to the plug on the tensioner and there are no numbers there either. I'll keep poking around and see what I can figure out.

Also, it's for both sides. I removed the seat belt tensioners from both yellow plugs, so just trying to figure out how to get it all back together.

Thanks for the schematics, that should help in the hunt.

[StickMon]

So, referencing X275-X279.pdf, you pulled the wires from G12/13 to pins 1 and 2 of X10216/17, and they're all Black?

I'm fuzzy on what's "Generator, seat belt tensioner".
Obviously it torques the seat belt when high Gs are detected, but I don't know if it's a motor or a solenoid that releases spring tension.
It's not drawn as either. It's drawn as a resistor (or at least a resistive load) with some mystery box in series with it. Seems like an odd place for the mystery box to be a fuse.

Do you have access to a multimeter?
The next thing I would do is measure the resistance and do a diode check in both directions to see if it's asymmetrical.

[Shipkiller]

The 'seat belt tensioner' does exactly what it says it does. When the proper conditions are met, the pyro charge is enabled and draws the seat belt tight over the seat occupant.

I would be VERY, VERY hesitant putting an ohm meter on that portion of the circuit. You might just fire the damn thing off….

[ANUSTART]

Originally Posted by Shipkiller

The 'seat belt tensioner' does exactly what it says it does. When the proper conditions are met, the pyro charge is enabled and draws the seat belt tight over the seat occupant.

I would be VERY, VERY hesitant putting an ohm meter on that portion of the circuit. You might just fire the damn thing off….

That was my concern as well trying that method. The "sure fire" way to make sure it all goes together is just order a new wiring harness. Looks like they run about $17 and come with the yellow connector. Then, just plug it into the tensioner. May go there route just to avoid accidents or hassle.

Here's the part… http://www.ecstuning.com/BMW-Z4-2.5i...Belt/ES143412/

[StickMon]

That was my other thought. Wasn't sure if it was a one-shot pyro.
In that case, it probably doesn't matter what polarity it's driven in, which is why both wires are black and it's drawn schematically as a resistor.

[Shipkiller]

For the yellow connector (X275/X279) pinout, look at the center of the PDF for Z4 Passenger Seat.PDF..

That has the pin locations on that connector.

[Shipkiller]

Why not do this:

Disconnect the battery, now disconnect the cable from the seat belt tensioner on the other side of the car, then disconnect the X275/X279 connector. Now that the circuit is safe, ohm out that cable for proper pin placement. According to the schematics, they are wired the same....

[ANUSTART]

Originally Posted by Shipkiller

Why not do this:

Disconnect the battery, now disconnect the cable from the seat belt tensioner on the other side of the car, then disconnect the X275/X279 connector. Now that the circuit is safe, ohm out that cable for proper pin placement. According to the schematics, they are wired the same....

I could use this method to identify the pins coming from the car and match those to plug 9 & 10 on the seat plug, just not sure how that would relate between the black wire and the yellow plug.

Below are a couple photos that may better illustrate where I am with this. If I'm misunderstanding let me know.

Originally Posted by StickMon

That was my other thought. Wasn't sure if it was a one-shot pyro.
In that case, it probably doesn't matter what polarity it's driven in, which is why both wires are black and it's drawn schematically as a resistor.

If that is the case, would be great. Just want to make sure that's correct before getting it all back together. If it is, sure makes all this much easier.

[StickMon]

It almost has to be a thermal igniter, like a flash bulb.
All it needs is for current to flow through it, overheat it, and ignite the charge.
Doesn't matter which direction the current flows.

Especially since it's a safety feature, if it mattered they would make darn sure it got wired correctly. Not only would the wires be marked differently, but the pins would probably be different, like opposite genders, so even if you were color-blind you couldn't wire it wrong.

[ANUSTART]

Originally Posted by StickMon

It almost has to be a thermal igniter, like a flash bulb.
All it needs is for current to flow through it, overheat it, and ignite the charge.
Doesn't matter which direction the current flows.

Especially since it's a safety feature, if it mattered they would make darn sure it got wired correctly. Not only would the wires be marked differently, but the pins would probably be different, like opposite genders, so even if you were color-blind you couldn't wire it wrong.

That's my gut on this too. Just want to make sure. I've taken out and put in these friggin' seats way too many times. I put in the M Sport seats and have had the airbag light on the whole time. I'm just putting the old seats back in and giving up the fight.

[WestCDA]

Originally Posted by ANUSTART

... I put in the M Sport seats and have had the airbag light on the whole time.

If you installed seats where the tensioner had already fired (not uncommon for seats pulled from an accident car), that will light the airbag warning. You can tell if they have fired by comparing the length of the plastic 'accordion' leading to the buckle - it is compressed and considerably shorter than on a new one. New ones are around 80 bucks online, IIRC, and very simple to install (one bolt).

[Shipkiller]

Originally Posted by ANUSTART

I put in the M Sport seats and have had the airbag light on the whole time. I'm just putting the old seats back in and giving up the fight.

What year are your sports seats? If they are the newer style, then the Passenger Seat Mat (PAM) interface is different than what you have on your 2005 and you WILL get an airbag light.

Just to make sure there is no ambiguity, when/if you put your old seats back in the car, you will have to have the air bag light reset. It will not reset on its own.

[ANUSTART]

Yeah, that was exactly the problem. They were from a 2008. I am going to put the 2005 seats back in and have the light reset. Fun times!