Junius

Hello everyone, I just bought a beautiful 2005 Audi A8L and there are some things that do not work. The fuel door button, when pressed, does not open the fuel door. The sunroof, even when the switch is turned, does not open at all. The ambient background lighting for the front passenger door trim does not come on at night time, as well as the window switch, which neither goes down or up when pressed. I can make the passenger window go down from the driver's master switch when I press it. When I took the car to the dealership for an inspection, they said the battery failed their battery test. Could this be the source of the problem? I've searched the archives but haven't found a direct solution. Any help/advice would be greatly appreciated.

jlbell

Sounds like the battery module cutting power to non important modules to conserve starting power. Check out the D3 tech dumb for more information about battery conservation. I am not sure which document it is but I know it is there.

D3 Tech dump - A8 Parts Forum

MP4.2+6.0

Yes, can well be a battery. D3's do weird things when battery is headed south, both due to power management system intentionally shutting off non critical loads, but also modules just starting to act flaky. If battery is more than 4-5 years old, replace it. When not if on a battery with a car, and yours at 10-11 years old might even be ready for its third battery.

I would focus there before troubleshooting other issues, especially with dealer already telling you that. On a 10 year old car, yes some of your other buttons may not work, but get battery out of the way so you can then assess more accurately.

Junius

Is there any specific or special adaptation needed to be done when replacing the battery?

MP4.2+6.0

You are supposed to put the identifying number in from the new (dealer) battery to get the power management system to reset. The work around if you buy a non-dealer battery is just to change the last digit of the prior battery by one. Easy to do if you have VCDS. If you don't have it, you won't be the first to just bolt it in and drive. The informal sense is it probably figures out after a while your battery is in better shape even if you don't enter a new battery number. It does figure out in the other direction that it is deteriorating as part of its normal function.

Junius

Thanks everyone, I will try to replace the battery as soon as possible (even though the car starts fine every time). Is there a specific battery that the A8 needs or requires?

TSHong

I would get a good quality battery name brand battery. each manufacturer will have a specified battery for your A8. Also invest in a VCDS cable so you can do some adaptations for all sorts of things. I see you got the D3 bug, congrats.

PM me if you want a 2008-2009 Nav DVD. I have the one from my 05 that I can give you if you have a 2005 Nav DVD.

Junius

Sounds good TSHong. Yes, after driving your A8, I had to get one, even though its not the w12. I'll look and see if it still has the original cd, which it probably does.

MP4.2+6.0

There are two sizes, which seem to jump around by both year and motor in a not totally coherent way. Either one fits, one being bigger in the long dimension than the other. You can look up which yours has, or just take a ruler to it and look at the specs for the two. Some just go for the big one even if they had the other. Group 49 and 95R.

Junius

ok thanks everyone! I will report the result when the car gets here next week from the east coast.