Hi I have just bought  a 2009 Audi A3 Cabriolet 2.0tdi 8P

Its battery goes flat overnight even having changed the battery. I have bought a multimeter and am learning to use it!

Once the car is locked and gone into 'sleep' mode it is drawing 760ma which is way higher than the 50ma max.

So, today, we have gone through testing all the fuses for voltage drop and found where the draw is coming from. The two suspect fuses are :

in the dash..fuse F16 which is for the aircon/climate module and obd2 diagnostic port.

in the engine bay: fuse F6 instrument cluster.

If i remove the fuse F16 the draw drops down to 30ma (which I assume is acceptable range) and then when testing the fuse F6 for the instrument cluster it then shows no voltage drop so no current going through it.

If I remove fuse F6 on its own it also drops down from 760ma to 30ma.

So I am assuming there is some link between the instrument cluster module and the climate module??????

I am leaving fuse F16 for the climate module out overnight to see how the draw is affected in the morning.

Would this point to a problem in the aircon/climate module wiring? It had a new blower fan fitted 8 months ago apparently.

What would be my next step with this?

Thanks for any help!

Michael.

Two points which may or may not have a bearing on your problem:

1/ Did you have the new battery coded to the car? It needs to be for proper functionality.

2/ A3s often had faults develop in their instrument panels. The cluster can be repaired for a few hundred pounds or replaced with a new one from Audi for many times the repair cost.

Hi Cliff,

I havent had the battery coded to the car. I have had the problem with the battery that was already in the car and the 'new' one (which is actually a spare battery that I keep topped up) is just in temporarily. When I get to the bottom of this problem I`ll buy a new battery and code it in( I think I can do this with carista.) I wouldn`t have thought not coding the battery would cause this problem but I would love to be wrong!!

I wondered about instrument cluster faults ( I had this problem on 2 fords and paid a huge amount for a new one form ford whilst abroad and then had the second one done for a fraction of the cost!)

I ran carista and it has in its memory an instrument cluster fault but it appears just once i think 9 years ago at a much lower mileage of about 27k, its now done 68k. I'm new to carista so I`ll post a screen shot if I can to see what you think.

thanks for your response!

I know nothing about Carista or similar OBD readers, so let's hope someone else can chip in.