2 stage airbag wiring advice needed

[Jonttt]

Ever since I've had a Z3 I've wanted to change the steering wheel for one that is slightly smaller (to stop rubbing against my leg) and has a better "feel" ie thicker.

There are plenty of options but none that retain the airbag system. Call me soft but airbags are one safety device I would rather not be without

People have fitted later BMW airbag wheels but they require significant re engineering to fit the Z3.

The only viable option to me is one of the Raid sports airbag range of steering wheels from Germany.

These are "generic" wheels that can be fitted with adaptor rings to fit various makes of car. They are a very popular mod to Porsches etc.... Unfortunately they are also very expensive (especially with the current euro exchange rate).

So for the past year I've waited for either the exchange rate to improve or a second hand one to come up on eBay.

I recently sourced a mint 6 month old 340mm "Daytona" wheel from eBay that had been fitted to a Porsche.

Nb. The OEM wheel is 370mm and you can get 340mm and 320mm but I have read that 340mm is the size to go.

So I ordered the Z3 "adaptor" kit from a company called Chrome Design in Germany who are a Raid main agent. The kit includes the hub adaptor to fit and a wiring harness to fit the airbag system.

Mike Fishwick did a great article some time ago about fitting a Raid wheel to his Z3. You can read it HERE. However Mikes Z3 is pre 04/99 production and so had a single stage airbag fitted. All cars made after 04/99 came with a different 2 stage airbag system and totally different wiring.

The adaptor I ordered from Chrome Design was for a "2 stage system".

I received the adaptor kit today and hope to have a go at fitting it this weekend.

However, when inspecting the adaptor harness for the airbag its pretty obvious that it is the same one as for a single stage airbag.

Therefore the Raid bags must all be single stage.

As my technical electrical knowledge extends to wiring a plug only I thought I had better ask for advice here before I start chopping wires and setting off the airbag

Here is the Raid Daytone Airbag (note there are two Horn buttons in silver)




Here is the back of the Raid wheel with the airbag adaptor wire fitted (but without the hub adaptor on). This just creates two "spade" connectors. Also note the 2 horn button wires which fit to a spade connector "block" (not shown but I can just plug in spade connectors from the cars horn wires).




Here is a picture from the back of an OEM 2 stage airbag Z3 (ie this is what I'm expecting to see when I take my current airbag off)




And here is a close up of the connector from the car



Now is my query:

I effectively have 4 wires coming from the steering wheel being

1) Horn Live (Red)
2) Horn Earth (Black)
3) Airbag Live (Green/White) ?
4) Airbag Earth (Black/White) ?

And 3 "pairs" wires from the Car (ie 6 wires in total) being (based on Bentley Manual these are)

5) Brown/Red = Horn +ve
6) Brown/Black = Horn -ve
7) Yellow/Black = Airbag stage I +ve
8) Yellow/Brown = Airbag stage I -ve
9) Grey/Black = Airbag stage II +ve
10) Grey/Brown = Airbag stage II -ve

nb I would have thought the airbag wires with the black stripe were -ve and brown stripe +ve but Bentley has them the other way around?

So its pretty obvious (I think) that for the horn I need to connect:

1&5
2&6

but how should I connect wires 3 & 4 ?????

Do I just connect:

3&7&9
4&8&10

My understanding is that the 2 stage system just means that the airbag deployment has 2 firing signals. The difference being the severity of the collision dictating how "rapidly" the airbag is deployed ie if moderate collision stage I is fired, if severe collision stage II is fired deploying the airbag more quickly. As the airbag will be single stage I need it to fire if either stage I or stage II is triggered so my logic is that if I connect the wires as above which ever stage is fired it will trigger the airbag which is what I need.

But is my logic correct????

Ideally I would like to retain the current OEM connector in case I ever revert back to OEM wheel (ie so I can just plug it back in) but this is not crucial if I need to cut the wires.

nb I know I have to disconnect the battery (in fact its not in the car so I will do the install before fitting the battery back in the car).

[peterandjenny]

I tried to find out how to fit a 99 m wheel to a 97 car and due to not being able to find out the exact wiring diagram sold it and brought the correct wheel

[gookah]

don't know what your worried about, it's not like it's life or death

[Ian_C]

Your logic sounds correct to me Jonttt so long as you've got the wire colours and +ve and -ve labels right. Presumably you've asked Raid for advice on this?

Are you sure that the plug from the car doesn't fit the plug on the Raid wheel and it's simply a case of plug n play?

[Jonttt]

oops double post

[Jonttt]

Thanks MyRedZed

I will be emailing both Raid and Chrome Design tomorrow.

The plug definately won't fit as the airbags is much smaller and only 2 pin. I got it with a Porsche hib adaptor and adpator harness (the wheel was fitted to a Porsche). The Porsche adaptor does seem plug and play in that the horn and airbag wires go into a connection block that looks like it would just plug into the Porsches. Thats what I was expecting with the Raid wiring adaptor rather than it just terminating in two "bullet" connectors

I need to check with Raid/Chrome design that they have not sent me the wrong wiring adaptor harness ie single stage instead of 2 stage (the actual hub adapator will be the same) ?

Now that I know the airbag is single stage even if there is a 2 stage adaptor all it could do is effectively what I propose above ie connect the 4 wires to 2 (there would just be no uncertainty if it was all pre wired to a connecting block like the Porsche).

[Brian H]

Hi Jonttt,

I had a look at the ETM for you type of car, You are correct with your wiring however the ETM shows the airbag stage 1 & 2 pairs connecting to an airbag diagnostic module. I would assume that both of these circuits are monitored.



GE = Yellow
SW = Black
BR = Brown
GR = Grey

As stated above Raid would be the people to advise on this as you would be effectively making a circuit redundant.

[c_w]

I wouldn't join up both pairs, I can't see that working for either the airbag module checking (airbag light will probably stay on) or to actually activate the bag.

I would bridge either wires 1&2 or 3&4 and use the remaining pair to the RAID airbag. The RAID airbag connector pins are perfect for PC 2-pin motherboard connectors (like HDD/Power LED wires), use a spare one of these to connect othe airbag then wire it to your selected pair from the car.

[estocks]

The airbag system monitors the resistance accross the wires, for opens or shorts,a and target load impedance. Shorting wires is not the answer. You may have to fit a load resistor of the correct values across whichever airbag circuit you don't want to use, and hope that both low and high fire in the impact of your choice.

[peterandjenny]

Having both airbags firing at the same time could be dangerous !
Spoke to an auto electrics place and they would not go near
airbag re wiring due to legal issues will be fitting m3 wheel at the weekend
good luck with yours it does look good .you allways have the option of not
enabling the airbag .

[Jonttt]

c_w (who has done this on his Coupe) has kindly emailed me what we think is the correct wiring adaptor (version 2 on the picture)



This look svery similar to the Porsche adaptor that came with the wheel ie seems to "bridge" one set of airbag wires from a 2 stage system with presumably a 3 ohm resisitor (ie under the looped sheath).

This would imply that the solution is to make one of the circuits redundant by fitting a resisitor to "fool" the control unit that it is fitted. The other circuit is then wired to the airbag.

To clarify a 2 stage airbag does not have two airbags but rather 2 "exploding" gas generators ie one "high" explosive for high impact collisions and one "low" explosive for low impact collisions.

So whichever circuit is made redundant then that gas generator will not work ie if the low impact circuit is not connected to the airbag then the airbag will not deploy if there is a low impact collision.

Logic would say that you would connect the high impact circuit ie deploy the airbag is big collision.

But if you look at the harness above it seems to use the yellow wires to connect to the airbag which according to Bentley Manual is "stage I" (I assume stage I is low impact and stage II is high impact but this is not clarified anywhere).

So I think the solution is to bridge the low impact circuit with a 3 ohm resistor and connect the high impact circuit.

This should be a simple DIY as all I'm missing is a 3 ohm resisitor and I can use the harness I have been provided (which I think is clearly for a single stage system )

But I'm in no rush and I should get what I paid for (I ordered the wiring adaptor for a 2 stage airbag system) so I will continue to persue Chrome Design who supplied it and Raid for clarification. (It would be nice to have the correct adaptor to take any "guesswork" out of which circuit and +ve/-ve to connect to the airbag.

One things for certain when I go to connect up the battery after fitting, the ignition will be in the on position and I will have my head in the boot

ps My brain still tells me that the best solution would just be to connect both circuits to the airbag but I don't really understand resistance and all that technical stuff and the harness above does back up peoples advice to make one circuit redundant.

[Jonttt]

Well here is the Porsche harness that came with the steering wheel.

On closer inspection (and having researched the above) it confirms that one airbag circuit is "bridged" with a resisitor.

Here is the harness (I think I should have been supplied with an equivalent but with a BMW connector block as per the above post):



and a close up of the "bridged" airbag wires after I cut off a layer of shrink wrap. You can clearly see there is a small resistor under there (I did not want to cut the fine layer of shrink wrap off as I can use this to bridge my circuit if the supplier does not provide the correct one).

[Brian H]

That makes sense Jon, you can see the resistor on the diagram above. I suppose it is the same principle as the passenger seat bypass!

B

[Jonttt]

Right I think I have got the logic worked out now

Further research into how the 2 stage airbag system works has identified a fundemental flaw in my original logic.

I (wrongly) assumed that the 2 airbag triggering circuits worked independently ie in a low speed collision stage 1 is triggered to fire a "low energy" gas cannister, in a high speed collision stage 2 is triggered to fire a "high energy" gas cannister.

Therefore I originally wanted to wire the single stage airbag to both circuits on the cars airbag triggering system. But this would not be possible as the control unit would sense a fault.

So I then thought that you had to choose which circuit to wire the airbag to and make the other redundant with a resistor. However, this meant a dilema ie do you want the airbag to fire on a low speed collision or high speed ?

The fact that the diagram above of a 2 stage system raid "convertor" harness seemed to utilise the "low impact" circuit to connect to the airbag only confussed the issue as logic would say that connecting to the high speed circuit was the thing to do but this would mean no inflation on a low speed incident.

The following explanation of the BMW 2 stage system clarifies:

"The cornerstone of the new system is a two-stage gas generator (as opposed to a conventional single-stage unit) which inflates the airbags. In less severe accidents only the first stage is activated whereas at higher severity also the second stage is activated either with a time delay or simultaneously."

The crucial clarification being that the first stage circuit is triggered on both a low speed AND high speed collision.

Therefore, the Raid airbag should be wired to the low speed circuit which will trigger the airbag on any collision (the 2nd circuit should be made redundant by bridging with a resistor).

All makes sense now.

So I can either make my own connection harness using the single stage one supplied and cannobalising the Porsche one (ie to use the wires with the resistor already fitted to bridge the 2nd airbag circuit) or wait to see if the supplier can supply the correct harness.

I can now fit this safe in the knowledge that it will work correctly and not have to "worry" about when/if it will work

I will do a seperate full write up of the install as my research could not identify a single source identifying how to fit a single stage airbag to a 2 stage system in the car.

Given that raid only produce single stage airbags and its the only "off the shelf" option to fit an alternative sports steering wheel and maintain an airbag to a "facelift" (ie post 04/99 production Z3) a full write up will hopefully save others having the same dilema as me

Final Wiring diagram I'm working to:

[c_w]

With this in mind I might check mine at some point as I cna't remember which stage I used!

[Jonttt]

Had an emial back from Raid themselves today:

**********************************************
From: Verkaufhp [mailto:verkaufhp@raid-rdi.com]
Sent: 05 February 2010 07:04
To: jonttt
Subject: AW: Z3 Raid Steering Wheel Adaptor Kit

You need the adapter atiwe 1220-1 for 2 stage Airbag

Mit freundlichem Gruß / Best regards

r.d.i. Deutschland GmbH
**********************************************

So confirms the picture above of the version 2 harness is the correct one.

I've asked Chrome Design if they can supply this.

They originally told me which adaptor I needed for a 2 stage airbag system.

The adaptor kit included both the hib adaptor and wiring adaptor. So I don't know if there is a seperate "kit" with the same hub adaptor but wiring adpator 1220-1 or if you are supposed to get the 1220-1 seperate anyway (ie the hib adaptor is only available with the single stage wiring adaptor?)

Either way they should haev told me this.

I'll see what they say and pursue them for completeness but at least I now know how to fit and can do it myself.

[Jonttt]

To complete the story Chrome Design (the suppliers of the adaptor kit) have emailed to confirm that they were not aware that the 2 stage system required a different wiring adaptor and that they cannot supply another kit or the correct wiring adaptor. They have offered to give me a full refund including postage costs.

I've decided to keep what I've got as its an easy DIY to "adapt" the harness provided and if I do sned back I would still need the hub adaptor and wiring adaptor which would probably work out more expensive.

So if you are purchasing a raid airbag wheel for a 2 stage (ie post 04/99) Z3 you either need to purchase from Raid direct and order the correct wiring adaptor and hub adaptor or get the kit I bought and just wire in a 3 ohm resisitor

[Ian_C]

...and just wire in a 3 ohm resisitor

Have you confirmed that the resistance required is 3 ohms jonttt? Might be worth checking your existing wheel when you remove it

[johnjo]

DO NOT try and measure the resistance of the airbag. The voltage from your multimeter could trigger the bag. I have used a 3 ohm resistor in the past to "fool" airbag system and it worked fine.

[Jonttt]

I am working off others who have mostly fitted non airbag wheels (the coupe guys are hardcore ) and successfully used 3 ohm resistors to "fool" the control system into thinking the airbag was still fitted

Come to think of it though I am going to use the wire used in the Porsche adaptor I have pictured above. I have not removed the final layer of shrink wrap so I probably should to check its a 3 ohm resistor as Porsche may be different.

Worst case though if I get that bit wrong is I get an airbag light that needs resetting ie the airbag should not deploy if the control unit sees a problem.

I don't own one of those electric measuring thingy majiggys anyway

Don't worry though I will still have my head in the boot when I connect the battery back up

[Titan]

Don't worry though I will still have my head in the boot when I connect the battery back up

That's OK
But who is going to be first to turn on the ignition?

[Jonttt]

The ignition will be in the "on" position when I connect the battery (no flies on me )

[Titan]

(no flies on me )

So how do you take the p1ss ?



(not that I ever would you understand)

[Jonttt]

Update:

Wheel fitted today and works perfectly.

All I can say is WOW, best mod I've ever done

I'll start a new thread with a full write up when I get a chance.

Thanks for the help guys, would not have figured out how to fit by myself