Flat Battery - Amp Problem?

Steveredman

Steveredman

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Hi,

For the last 2 days I've got up to find my car has a dead battery.

The AA came out both times, jump started the car and tested the battery with the result being that the battery is fine.

The only conclusion I can come to is that something is draining the battery overnight. The AA guy today put his amp clamp on whilst I switched the car off and it still showed 10A drain. As the last item I replaced was the radio module (DAB upgrade) I unplugged this which dropped the drain slightly to 9.5A. I then tried unplugging other devices, the biggest drop came after unplugging the cable from the Bose amplifier.

My questions are:-

Should the amp drain that much power (must have been over 8A) whilst the car is off?

Is it likely that the amp would reduce it's drain after some time (wondering if it remains in a powered up state for a period after the car is stopped)?

Is it likely that the amp is faulty?

Thanks for any help!


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Could it be that the DAB module was from a non-Bose car?
If so, I suppose it might not be controlling the Bose amp as it should be, turning it on and off as it is meant too.
Might just be a coding issue?
 
Sounds possible, I was under the impression that if it was from a non-Bose car then I wouldn't get any sound, but perhaps only the reverse is true.

Do you know where I could find the coding? My local garage are a bit busy but they might let me use their VCDS for 5-10 mins if I ask nicely.


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If the module came from a Bose car and yours didn't have it, you wouldn't get any sound, but I don't really know what happens if it is reversed.
B5NUT coded mine for me, but I'm not sure where he got the info from, sorry. Maybe drop him a PM.
 
Thanks for that, I've PM'd B5NUT, hopefully he knows where the info is.


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If the coding was wrong the internal amplifier would be enabled on the Radio module resulting in no Sound.

When you say the current dropped when you unplugged the AMP how much did it drop by? You have to remember it takes about 5-10 minutes for the car to go into sleep mode. You would have to wait for all the system to power down before checking for a current drain, so don't open any doors or press any button on your fob as that will start to wake the car up again.
 
If you are 100% sure that running it in non-Bose mode disables audio on the optical connector then fair enough.

I have followed the process my garage mechanic suggested:-

Open boot, latch boot to make the car think it is closed.

Disable internal alarm sensors and close the door and lock it.

Wait some time to allow systems to shut down.

Carefully remove the battery terminal clamp whilst keeping a constant connection with a multimeter set to measure current.

The results I have found are as follows:-

With everything connected I see a drain of about 8A, it fluctuates a little.

I keep hearing a relay click twice in the right hand side near the fusebox. When it clicks once the current drops sharply, the second click which comes straight after sees the current come back up again.

If I disconnect either the large connector from the amp, or the optical connector I hear the relay click once and the current drops. If I replace this connector the relay clicks again and the current rises as well.

For the time being I intend to leave the amp disconnected overnight anyway. I could try swapping the radio module back to the old one, I'm presuming this won't lose my component protection removal?


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Can you post a picture of your Bose AMP.

What I would do is unplug the Bose AMP, then the next day unplug the radio. If one of them works then you know which is causing the problem, if both work then it could still be either module, what you will need is one of these http://www.ebay.co.uk/itm/FEMALE-MO...819294?hash=item41b84b565e:g:z6oAAOSw44BYNERu
so the MMI system is still functional even if one of the modules is removed from the MOST optical loop.
 
acf127fcf8bb4f319fc05f61159db8b1.jpg


1d18ad2182afa8334bdeedd9cc9fd133.jpg



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I jumpstarted a colleague's car on Friday, could I have damaged something in the process? What I did was to hook it up with my engine running to put some charge on his battery before disconnecting and starting his car. Could the extra load have caused damage?


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Did you connect direct to your battery, or the terminals under your bonnet?
If you connected to your battery, I think that there is a possibility that you may have damaged something.
 
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I used the terminals under the bonnet


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I jump started the guys car on Friday morning, the car first went flat on Saturday night


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Starting to look like that has caused issue, as it's properly taken 24/28 hours to flatten a fully charged battery, as it would take around 18 hours to fully charge the battery from flat..

Don't know why but Audi's are very temperamental at being or being used for Jump starting.
 
The question is what would be likely to be damaged? I left the amp, radio and the unit between them unplugged last night. Just gone to start the car now and it was fine. Plugged them in and the battery was at the same level it was last night before I unplugged them. I have left everything but the amp plugged in now, will check it in an hour or so.


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With the modules unplugged the MMI system would be dead, it could even be the 5F module not shutting to the other modules on the MOST bus, I would get a loop cable and isolate each device in turn.

I take it there are no fault codes showing up when you scan the car.
 
All the fault codes were related to the battery going flat when I checked, I cleared them the other day so I'll scan again now I've been for a few drives out. I'll order that MOST loop and probably an amp clamp too as trying to take the battery terminal off whilst keeping the circuit intact with my multimeter probes is very tricky!


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Ok, I now have the loop connector and a clamp meter. I have already ruled out the new radio unit as I took that out first, disconnected the power and used the loop to bypass it. Problem still exists so moving on to the next item - amplifier.


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I have non bose amp and my battery was drained too and local dealer for audi after 1 day searching for problem says to me that amp is not shuting down after car is locked so he tell me that is problem in amp so i tested it a little i locked car and then leave it for few hours and when i unlock it and i touch amp module in trunk It was so hot that I almost burned my hand.

So i am wondering is there any easy fix for that or i need to replace amp? If i need to replace do i need to code it if I buy same amp as mine (non bose)?
 
You will need to buy the same model amp, and you will need to remove component protection.
 
Certainly seems to be, I disconnected it and used the MOST loop to bypass the amp and the battery drain disappeared. Seems to be a common problem and bizarrely coincidental timing for me, unless I provoked it by the various times I disconnected stuff whilst doing my DAB install?


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Interesting this is the first time I've heard of this on a 3G bose amp. That link look good, would be interesting to see how much they charge, to fix the power fault.
 
Looks like it's a flat fee of about £200, definitely cheaper than a replacement + CP removal. Still quite dear though, I'd have probably tried heating the board to re-flow the solder but it's coated in some kind of sealant, would need to work out how to remove this (and have a method to replace it) before considering any surgery.


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B5NUT said:
You will need to buy the same model amp, and you will need to remove component protection.
Click to expand...
B5NUT i just found very afordable amp (non bose)with part number 4F0 910 223 B and my amp part is 4F0 910 223 M so i dont know what last latter B or M means?? will this with b fit in my car
 
As they are a physically different units I cannot say if what would work, you would need to see the pinout of each AMP and compare them.
 
May have had water ingress, the washer pipe bend (into the bootlid) for the Avant sits above those units, splits and leaks.

Check the area for water.
 
That did come to mind but there is no sign of water in the compartment and no visible damage to the board inside my amp so I'm certain that this wasn't the cause in my case.


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That water issue was fixed on facelift Avants
 
Last edited:
That's good to know. Rules one potential cause out.

I'm a bit confused with mine, I found that leaving the amp unplugged overnight was a good workaround to stop the battery being drained. Last week I was working away and my hotel was in walking distance of the office so my car didn't move all week. I parked up on Monday morning and unplugged my amp, on Friday afternoon I started the car with no problems and plugged the amp back in.

Last night when I got home I forgot to unplug the amp, however the battery did not die. When I used it today the battery was reporting full charge. Maybe the problem has 'cured' itself?


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