TT Bizarre cabin electrics

I need some help to diagnose the root cause of the bizarre things that are happening with operation of the cabin electrics my 2003 Quattro Roadster. The story goes like this.
First the average fuel consumption started providing bizarre readings, jumping from 12 to 45 litres/hundred kms and then just rolling out wide ranging readings while the car was stationary with the engine running. All other dashboard information is perfect, except distance to empty, which varies with the reported average fuel consumption.
Next, the Bose audio decided it had lost power and went into safe mode. Since it was re-activated with the security code, about a week ago, it has worked perfectly.
Most recently the auto feature of the passengers door window stopped working, both up and down. The movement of the window was fine if the switch was held. This morning the auto feature was working perfectly again.
All this time the average fuel consumption readings have continued to come from another planet. The car runs perfectly and all other dashboard information, date and time, audio system information, average speed, spot fuel consumption, etc., including the test function appear to be operating normally.
I am concerned that a visit to the Audi Centre could result in a very expensive diagnostic effort without actually identifying the real fault. All ideas gratefully received.
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my only guess would be that all the problems are coincidental.
The fuel metering may be a sensor that's gone TU. Also those all electronic panels have not got an excellent track record as they age.
dj A4 1998 2.4 V6 SE with a fading instrument panel on warm ambient days...but she's closing on 100K and runs every day like a dream.
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Hi Lester,
On Sun, 27 Sep 2009 13:19:01 +1000, Lester Burnham

[Various electrical stuff]
How old is the battery?
I've seen a few Audis behave strangely (Airbag warning lights and many more) with old batteries.
The BOSE and the loss of memory of the window switches points me to an intermittent brownout of the electrical supply => Old battery.
Those batteries might still have enough juice to fire the engine but for whatever reason the play havoc with the electronics.
Try a new one.
Regards
Wolfgang
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Thanks Wolfgang, it is the original factory fitted German battery from 2003. Its longevity was the subject of discussion only a few months ago. I will swap it out and see if that makes a difference.
Regards,
Lester
wrote:

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On Tue, 29 Sep 2009 08:18:02 +1000, Lester Burnham

Ouch, I think it's time to replace it.
Would be curious to hear from you what it was in the end.
Regards
Wolfgang
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Wolfgang Pawlinetz wrote:

I'd consider swapping the battery as Wolfgang suggests, then a scan with VCDS in case the convenience ECU is upset.
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Well, it was all looking very fine this morning although it is still on the old old old battery at the moment. I am just returned from a week away, without the TT, which was left on a trickle charger. The battery was very low when I left. When I arrived home last night I swapped it to the regular charger just to be sure the battery had every chance to be fully charged. This morning it was 100% according to the lights on the charger. The car started easily and ran around town happily with all systems functioning as Ingolstadt intended. Tomorrow when I have time I will stick the volt meter on it to see where the battery is after standing for a day. However, I will get a new one as soon as I have a moment regardless; 6 1/2 years is a good run for a battery... but it is German.
Further (final?) update when I have the new battery.
Thank you all for the benefit of your experience and expertise.
_______________________________________________________________________________
wrote:

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Well, after a good charge the old battery was held up well and the bizarre behaviour of the digital readouts, particularly average fuel consumption, stopped. Now with a new battery installed everything remains fully operational and I trust it will remain so.
Thank you all again for your sharing your experience and expertise.

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On Mon, 19 Oct 2009 06:10:26 GMT, Lester Burnham

Glad it worked out so easily.
Enjoy that fine car, Lester!
Regards
Wolfgang
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