Hello everyone, I have a 2007 Audi A3. It has a brand new battery and the alternator has been tested, but the battery is not getting charge. The thermostat and thermostat sensor was recently changed and the alternator was removed. Thanks in advance for any advice. 

Hello Nick,

It’s unlikely that you would have needed to code the replacement battery on this age of car, so probably wise to ignore that possibility. 
What we need here is actual voltage readings:-

Battery voltage at rest ( after it has been independently recharged). Should be around 12.4 ish volts.

Charging voltage at the battery with the engine running at around 1500 rpm. Should be around 14.5V. 
 

Please let us know what the readings are.

Regards,

Gareth. 
 

If I may disagree with one of Gareth's points, my own 2007 A3 did require the battery to be coded to the car so it would be wise to do this first. However I have a feeling in this case that something else is wrong.

Being parked for less then 24 hours the new battery drained to 40%. Also 💯 the battery has to be coded and the power steering also recalibrated. The issue is that the alternator is not sending charge to the battery, but the battery is new and the alternator checked out good. 

Best to get it scanned on a decent code reader, and hope the discharge has not damaged the battery.

It was scanned and passed 

There is room for healthy debate here, since my understanding is that replacement batteries for pre 2008 vehicles VAG cars do not need coding. 
Possibilities with your A3 Cliff is that it was either a 2008 model year car, or x years on from new,  when your battery needed replacing, it was topical ‘common practice’ to claim they had to be coded. 
Nick:-

Who informs you at 100% certainly that the above is wrong? 
I appreciate that that is academic in your situation, since no doubt it has been coded whether it needed to be or not  - so as I said originally, you can eliminate that  as a possibility. 
Back to your issue - Have you actually measured the current drain on the car ( and incidentally, do you have answers to my original question)? Whatever it is, it has to be considerable, e.g. many amps, rather than mA, but you need to know. 
Possible culprit at that level of discharge would be discharging back through a faulty alternator (diode??).

Yes, I know  you say it’s been checked, but you don’t give us any figures to work with. 
Regards,

Gareth. 

 

30 minutes ago, Rugrat22 said:

It was scanned and passed 

Hi I would be more inclined to aim at the wiring loom going to the alternator as they generally get a bit crusty at that age and chances are there is a break in that part of the loom which is possibly short or to ground, it won't show up on the diagnostics as back then it was not monitored and what makes me think that is the alternator was removed thus disturbing the wiring.

Steve.

Thank you!! This is exactly what we are leaning towards!