Battery drain A8

[Dusko]

Car: A8, D3 platform 4.2 quatro

I have battery drain issues, it drains 10.0 amp/h for some reason. ( Batterty is new, but it was same with old one wich means old battery was good)
It drains full battery i cant even start engine, battery goes to zero energy.

Anyone had similar problem, to give me advice what to do.

[EG-4.0TDI]

10 AH is big for a drain - on that basis, you should be flattening the battery 10 hours which suggests something fairly major is not switching off (door microswitches and small slights tend to be between 1 and 5 AH drains).

When you lock the car the hazard light switch and the gear indicators (PRND) will remain dimly lit for about 10 minutes - check after 15 mins or so to make sure that have gone out. If they haven't it means that something is keeping the gateway awake. I would start by listening very carefully all round the car to see if you can hear anything running - for example the DVD sat nav drive in the boot can sometimes stay on which keeps the whole MMI awake (you can hear it whirring on the near side of the boot (nearside of a UK RHD car).

I also had an auxiliary heater fail to shut down which caused me a drain (you can hear the fan running behind the off side headlight (offside for a UK RHD car that is).

I'm not saying it's a failsafe diagnostic, but both of the battery drains I had were ultimately diagnosed by listening.

If you can't hear anything then you can start pulling fuses one by one to see which one stops the drain but this is rather more involved and will trip about a million fault codes that will then need to be cleared before anyone else can do any diagnostics.

[Dusko]

The thing is, i have drain battery issuses only when I start motor and it gets warm, i tought it wont drain if I put terminal off and back again( maybe something is not turning off so when i take terminal off it will stop), but if I put it on again it still drains untill it drains battery to zero energy. If i pull out battery for charging and put it again in it wont drain ( motor is cold again) till tremperature is up, after 10 minutes of constant work it starts to drain again.

[Micha_elD]

Mine will drain at around 6-8AH when I'm near the car, but it drops when the car is locked and I'm moved out of range. The Advanced Key (keyless locking and ignition) is the problem here, in normal use there isn't a problem, but when I'm working on the car it fires up all kinds of things I don't need, until it flattens the battery after a few hours.

If you have Rear Seat Entertainment and TV that is quite a heavy drain, it keeps the TV tuner on to supply the rear screens, even if you aren't using radio or anything coming out of the speakers. Again, it stops when the car is locked and you move out of range (a couple of metres or so).

So, testing for the problem could be a problem if you have advanced key