Airbag wiring diagram

[Phil Self]

In my RS2, I need to check the wiring from the airbag sensor which is located on top of the propshaft tunnel under the dashboard, up to the airbag warning light on the dashboard and to all other positions. Maybe it's because I'm a simple countryside ape that I can't pick up the info from the ABY/ADU guide by Paul, or is the airbag wiring in another part of the forum that I haven't found yet?

All help gratefully accepted,

Regards,

Phil Self

[adam g]

Im guessing you are trying to diagnose the reason the light is on. Even if the RS2 only has frontal driver and passenger bags you are looking at a few cicuits incuding all the sensors. Would be easier to look at the fault codes to see which circuit us down.

Sorry i dont have a diagram.

[johne]

This is the link to the circuit for for late models ('96):

http://www.s2central.net/S2_Schematics/C/C75.PDF

but there are others depending on if you have seat tensioners etc.

The airbag wiring is very simple because there aren't any external sensors. The actual crash detection sensor is inside the airbag module under the dash and the wiring is just power, the dash indicator light and the lines to blow the airbag(s).

John

[adam g]

Wow that is an old skool system but I guess airbags were fairly new in the industry back then.
Be careful with that module and disconnet the battery before removing or checking circuits. Also dont put a meter across the module terminals as some if the old ones could be triggered by a meter.

[shaun5]

Ive got the air bag light on on both my S2 and 2.6 coupe. I disconnected the wires yesterday and nothing went off i made sure i was clear of the air bag tho.
I assume you could fix the fault but will need to reset the light with VAGCOM?

[johne]

It's possible that just resetting the light will clear the "fault". Happened on mine once, the Dealer reset the light and it's never come on again and that was years ago.

You will need Vagcom to "talk" to the airbag controller and reset it. It would appear from the experience of folks on here that establishing a connection to the airbag unit is one of the more difficult ones to get to work using some of the many variations of connection hardware and software out there. Old posts on the topic will help you.

There was also an Audi recall around 1998 that involved fitting an extra earth strap to the steering wheel iirc - could be worth checking if it applied to your car(s).

John

[shaun5]

Good info there john

[Phil Self]

Airbag wiring diagram

Thanks to Adam, John and Shaun for all advice and info. This will all be passed onto the auto electricain who is doing the clever stuff, which is trying to eliminate the airbag light being on all the time. I've just noticed that my country of residence is supposed to be the USA; it's not, I'm in the UK. Must have pressed the wrong button when I joined the forum! The fault code reader didn't give error numbers but said "insufficient/intermittent voltage". We tried resetting a few times, with no change. When removing the sensor, I did have the battery disconnected, but I will mention not putting a meter across the connector to avoid the chance of setting off the airbag. My RS2 was built in November 94 and registered in the UK in March 95; as far as I know it wasn't recalled to fit an extra earth strap to the steering wheel. The link to the wiring diagram, sheet 75 for 96 year cars onwards is a step in the right direction, but has anyone got the same wiring diagram for the 94/95 cars, or can I assume that the info on sheet 75 is near enough? Or is there another link that I can't find for my year car? As before, all help gratefully received.
Regards
Phil Self

[adam g]

In my experience it is 90% of the time deterioration of connections/wires between the airbag module and the tunnel sensor that cause the fault. The electrical gubins inside the inflators is very reliable.
A lot of garages change them needlessly.

[shaun5]

So would disconnecting the plugs and checking the pins be enough or do you have to follow the wiring back through checking for damage?

[Phil Self]

Airbag wiring diagram

Anyone found the right airbag wiring diagram for a 94/95 RS2 please? It would be great if you have, as the auto electrician is coming round tonight.
Regards,
Phil Self.

[johne]

If you've got seat belt tensioners then it's the diagram at the link I posted earlier.

If you've not got seat belt tensioners it's either this:

http://www.s2central.net/S2_Schematics/C/C33.PDF

or

http://www.s2central.net/S2_Schematics/C/C09.PDF

depending on whether you've relay J312 for the warning light or not fitted in position 9 of your auxilary relay panel which is the one above the driver's footwell.

John

[Phil Self]

Airbag wiring diagram

Thanks again to Adam, John and Shaun for very good info. Tried disconnecting the sensor, checked if connections seemed ok, which they are. Then tried reset, but that didn't get us back to normal - airbag sensor light still on. John, we were in the garage when you posted the links for seat belt tensioners, so that's something to follow up.
Hope that next post will be to say problem solved.
Regards,
Phil Self.

[Phil Self]

Airbag wiring diagram

At last some success with the airbag warning light problem. To cut a long story short, I got another airbag sensor off ebay. I'd been told that although the part number on my RS2 is 8AO 959 655H, this had been superseded by 8AO 959 655B. Weird or what?Only Audi would think that B comes after H. Also I was told that the same part number was used in various other Audis, for instance the A4 and others that I can't remember, of about the same year as my car (made late 94, registered early 95), but using the whole RS2 part number, 8AO etc. The advice was to try both numbers in ebay and I got one with the B suffix for under a tenner, which came off a 95 A4. A lot better than about £280 or £360, if Audi had one, depending on which number they were quoting on, but it didn't matter as they couldn't supply anyway! A very important point, if you want one, is to find out from the seller if the sensor has been triggered in a crash. If it has it could cost up to £50 for a reset, providing that it's not been structurally damaged. I was a dummy and didn't ask the question before I bought it, but I was lucky, as it hadn't been triggered. The test gear that the auto electrician has is not the genuine VW, but maybe a clone from China, so it could do some tests, but wouldn't do a reset, when we were working with my old sensor, but as soon as we tried the new one off ebay, ping, the airbag light went out after a few seconds after start up. We never found out what is wrong with my original one. So provided that I don't stuff it up when I reassemble all the bits, all should be fine. Thanks again to all who helped with info and I hope that what I've found out could help some others. It's not the end of my electrical problems - see another post.

Regards,

Phil Self

PS can I be promoted to a higher rank than 'tinkerer' yet, now that I've got a few dozen bits to reassemble?