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2008 A5 3.0
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Discussion Starter #1
Hello,

i’m fairly new to this still but i’m hoping someone can help. I bought my about 8 months ago and everything was fine. Then at the start of the year it developed a battery drain. I’ve had it at 3 different garages 2 of which didn’t help at all! The third one told me there was an issue with the amp (bang and olufsen system 2g high). So the amp was sent off for repairwhen it returned everything was good for a few weeks but now it’s draining again in a few hours but there no major drain when testing the battery. I’ve replaced the radio box in the boot and the centre console controls. Bypassed the Bluetooth and sat nav but still no luck. Yet if I unplug the optical cables the drain disappears just have no stereo. Is there anyone who could help before I give up and scrap the thing?!

also the repair company are sure it’s not the amp and won’t have it back to test!!
 

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Get or make an optical loop. Then you can remove components from the optical bus 1 by 1 and hopefully identify the culprit
 

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2008 A5 3.0
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Discussion Starter #4
Get or make an optical loop. Then you can remove components from the optical bus 1 by 1 and hopefully identify the culprit
Thanks for the quick response so the sat nav and Bluetooth both currently have loops in. I tried this with the stereo box under the amp before replacing it but it makes no difference. is there anything else in the fibre circuit I can try to loop out?
There’s no fault codes stored apart from the fuel cap and door handle sensors.
 

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Is the amplifier fibre? I’d loop out one device out at a time and see if you can pin down the fault.
When you lock the car there is a few minutes delay and then CAN signals put the various modules in the car to sleep. Sometimes they can stay awake and cause your drain. Check for faulty or loose connectors. Measure the drain on each fuse when the car is “asleep” that may yield some answers.
 

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2008 A5 3.0
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Discussion Starter #7
Thanks. I’ll have a play with it tomorrow and see what I can come up with.
 

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Had a similar issue, turns out it was a faulty boot latch. The boot light was remaining on. Hopefully it could be something similar, otherwise it sounds like a parasitic drain
 

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Proper drain tests are time consuming as modules need to go to sleep fully before tests can be done. Also depends on how they are conducting the tests? Pulling fuses individually or measuring current draw across the fuses etc?
 

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As commented by @morski the best way to locate a parasitic drain is to methodically check each device allowing for "sleep" time.
 

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2008 A5 3.0
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Discussion Starter #11
The parasite test shows a 5 amp draw for a few seconds every ten minutes. There’s a relay that clicks in the boot every time it draws. I’ve tried pulling each fuse in the boot which doesn’t make a difference. It’s definitely to do with something in the fibre loop as when I unplug the fibre cable from the any of the modules the car will sit for weeks and not go flat. Is anyone able to tell me what else is apart of the fibre loop so I can try to trace it. I know of the amp, sat nav, radio module below amp and Bluetooth module under drivers seat.
 

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You cant do a proper parasitic draw by pulling fuses as you will wake the car modules up. There are test instruments that measure current across the fuses without having to remove them
Gateway is part of fibre loop
 

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It’s definitely to do with something in the fibre loop as when I unplug the fibre cable from the any of the modules the car will sit for weeks and not go flat.
You need a loop adapter. Use it to isolate ONE of the fibre modules at a time. That way you leave the other devices as part of the fiber network. This approach will help you determine if any of the fibre modules are causing the problem. Give that a go and let us know what you find out.
 

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2008 A5 3.0
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Discussion Starter #14
You need a loop adapter. Use it to isolate ONE of the fibre modules at a time. That way you leave the other devices as part of the fiber network. This approach will help you determine if any of the fibre modules are causing the problem. Give that a go and let us know what you find out.
Yeah that’s what I’ve got. I’ve tried it on the amp, Bluetooth, sat nav and radio but it still drains. I’m not good with electrics as you can probably tell. Are there any other modules I’ve missed I can loop out?
 

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2008 A5 3.0
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Discussion Starter #15
So I’ve been out in the car today and it’s developed another fault which I assume is related ? It randomly flashes parking brake fault, headlight adjustment fault, then after a few minutes I get an esp fault and all the other faults disappear off the dash? Once I turn it on and off all the faults disappear for a while. I only have OBDeleven so can’t post the full log but log faults
01316- intermittent - implausible signal
00473- static
01314-intermittent - implausible signal
 
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