Wiring Diagrams for A8/S8...

[SyncroS8]

Hi All,

Does anyone have wiring diagrams for a 2001 A8/S8?

I'm looking in particular for the engine wiring diagram, headlight wiring and brake warning wiring diagrams.

My S8 has a peculiar fault which I'm fairly sure is a 'bad earth' related issue but knowing where to look for 'that' earthing point will save me hours of tracing wiring!

Cheers

MG

[PsYcHe]

You checked the main one on the pillar behing the driver's front wheel arch?

[SyncroS8]

Nope but this is the kind of info I need

Any photos of it?

The 'odd' behavior is that the brake warning light comes on in the following circumstances.

When the car is cold, when you turn the headlights on... but you can turn the sidelights on without it bringing the brake warning light on.

The brake warning sensors have been hard-wired out so it's not that.

You can turn the headlights on once the car is warm (20 miles or so) and the warning light doesn't come on.

My thinking is that it's a bad earth and that the extra current draw on the circuit when the car is cold, when you first turn the headlights on and fire up the Xenons is enough to drop the current in the brake warning circuit and bring on the light... which then won't go off until you restart the car.

Cheers

MG

[PsYcHe]

It's on the chassis leg to the front of the wheel arch.. There's a thread somewhere with photos.. It gets corroded and just needs a clean and tighten

[SyncroS8]

Ok. Any idea what the thread was covering?

I've searched but come up blank.

Will keep looking...

MG

[Iyole]

Link to Wiring diagram.... Scuse the Russian.... but if you download the PDf
it has the full wiring diagram....

http://www.mitchell-auto.ru/wiring-d...udi-s8-wd.html

[SyncroS8]

This is why I love this forum

Wonderful thank you.

MG

[ainarssems]

The 'odd' behavior is that the brake warning light comes on in the following circumstances.

When the car is cold, when you turn the headlights on... but you can turn the sidelights on without it bringing the brake warning light on.

The brake warning sensors have been hard-wired out so it's not that.

You can turn the headlights on once the car is warm (20 miles or so) and the warning light doesn't come on.

This could be issue of battery getting old or capacitors within ballasts. Because of one or another or combination of both there is a voltage dip/noise in electrical system that throws up weird behaviour. I had similar isuues with aftermarket HID's. Battery was getting old and switching HID's on would stop CD changer working and dash froze up. I fitted caps to HID's and problem was gone. After some time one of the caps failed , I removed it and occasionally I would get the symptoms again with only 1 cap fitted mostly in colder weather or if car have not been driven for a while. In the coming winter I fitted new batterry as old one would go flat if car not used for more then 4 days. With the new battery problem is gone even after I removed the remaining capacitor.

But of course it can be just a bad earth or power connection. Check battery terminals as well.

[SyncroS8]

Update on this.

I haven't had time to look yet but the brake warning light comes on without having turned the headlights on but only when you press the brake pedal and only when it's damp outside

Does anyone have a diagnostic bulletin on the brake warning lights on this or text on how the system functions?

Thanks

MG

[Iyole]

Some food for thought .... Could be irrelevant....

http://www.audipages.com/Tech_Articl...nsorshort.html

http://www.audipages.com/Tech_Articl...akesensor.html



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