front seat airbag - why 4 wires?

[Goran]

Does anyone know why the front seat airbags have 4 wires, two of which are brown.

The TT seats I bought have only 3 airbag wires, only one brown wire.

On this diagram (for an S8 apparently) it shows only 3 wires for the seat airbags? Or maybe the ones I circled are not the correct ones?

[ainarssems]

The ones you circled are head(curtain airbags) not the seat airbags. Seat airbags would be the ones on the ones on right side with only 2 wires.

[Goran]

sorry for delayed reply, thanks!
I am now looking at this again. Strange how Audi wiring diagrams dont match the actual wire colours.
It now looks like the D2 seat airbag is single stage, but has two earthing wires?
The Audi TT airbag is also single stage and has one earthing wire. So looks like this will work.

Whats confusing me at the moment is that the Elsa wiring diagrams for TT Mk1 do not match the actual TT airbag wire colours. I have so far tried looking up all TT's from 1999 to 2004 in Elsa, they all say the seat airbags have the driver's = green+, white-
passanger's = white+, blue-

But both of my TT seats have airbag wires black, blue (and the brown earh is the same). Also all the TT Mk 1 airbags I can find on ebay all have black, blue and brown. So how the heck do I know which is + and which is -?

unless, of course, the wire colour is from the plug on the controller side, not the plug on the airbag side?

[notorious]

ELSA is very accurate with wire colours.

On screenshot I see wire colours BEFORE connectors T3h and T3i. AFTER connectors colours can be different.

All connector pins are usually clearly marked on connector itself. Use those pin numbers for guidance. For example: T3h/1 means pin number 1 of connector T3h. Just find pin number 1 on the actual connector.

[Goran]

Thanks, I will order a pair of controller-side connectors from A8parts, I'll need them anyway for a neat conversion.
Now just to figure out where the two brown earthing wires go from the D2 seat airbag (brown plug). Picture to follow tonight. If they just go to a earthing point in the car then no problem. If they go back to controller, then confusion. See Elsa doesn't have those wires on the diagram either. Maybe because they dont go anywhere?

[notorious]

Earth goes only to car chassis

[Goran]

Thanks Sergei,
So just to confirm, its the black plug from the airbag, that just goes to the chassis?
I cant find it in the Elsa wiring diagrams.

Thanks

[notorious]

>> its the black plug from the airbag, that just goes to the chassis?

Sorry, I stopped understanding what picture means what. Picture with airplanes in background is D2 seat or TT seat?

What is this picture again? Part of TT seat?




Two ELSA diagrams are clear to me.

If we assume that picture with airplanes in background is D2 seat, then red 2-pin connector should be T2ay or T2az according to last ELSA diagram provided. It has two pins and it is red colour.

Then we have some earth wires on the picture, but it is not clear where they come from.

I appreciate earth wires go to black connector. I have no idea what black connector is. Black connector may not be relevant to airbags system.

[Goran]

Sorry, I forgot to label the pictures. The airplanes picture is the D2 airbag.
sorry, bad quality picture, it has two brown wires to bolt to airbag casing, and these are spliced into the airbag loom, but have a separate black connector.
I may need to confirm with A8 parts where this goes in the car.
The confusing thing is that its not in the Elsa airbag diagram, even though wires bolt onto airbag.
Maybe as you suggest its just earthing wires, and maybe they are represented in a different Elsa diagram.

[notorious]

Is black connector a single pin connector? If yes, it should connect airbag's local earth with global 'big earth' of the car chassis. Just like T1p or T1q connectors on D2 ELSA diagram.