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Hi

So I had some weird battery issue. Lately, I noticed that the battery discharged if the car was parked for more than three days. I was trying to investigate. I do computers and math but not very good in electrical engineering. Please bear with me.

The battery was replaced a year ago with a OEM one from the dealer. The previous one was in the car for 11 years. So I assume that the battery is fairly new. I checked the alternator and found that it works correctly and provides expected voltage. I did it with the voltmeter and with the VAGCOM tool. Both shows expected voltage.

Some people reported issues with power regulating module. One posts stated that I should upgrade module and MMI software at the dealer to solve the issue. But I will leave the rather paranoid subject for later.

In the meantime I have tried to see if there is a current drain while the car is parked. I disconnected the black cable from the battery and attached the amp-metering gadget in the middle.

When the car was unlocked, the gadget showed 5A current draw. When the car is locked the gadget shows 0.97A. Which expected to drain 100A battery in about 100 hours (4 days) which is consistent with real life observation.

So I started pulling one fuse at a time and see which of them is responsible for the current drain. The consumption dropped when I disconnected 30A fuse F24 in the rear fuse box. With the fuse disconnected the consumption was about 80mA. Which I guess is normal.

According to the records, it is “Audio system – digital sound system control module”. I guess this is the amplifier in the left side of the Avant’s trunk. Something in the MOST loop keeps the amplifier up. Or perhaps the amp got corroded with the washer fluid dripping on it.

I have X-Car MMI Audio adapter for a bluetooth which is an aftermarket and is a suspect. But it was there for years without any side effects.

I also have the Bluetooth phone module flooded and removed from the footwell. Perhaps there is a residual stuff on the connector in the footwell. I will check tomorrow.

Otherwise, I am back to the paranoid subject of the power regulator module does not communicate to audio control module and the audio control module does not go to slip properly.

In the meantime, I decided to simply keep the fuse out when the car is parked and see if this solved the issue.

Richard Levy

You answered your question.

"Or perhaps the amp got corroded with the washer fluid dripping on it."

Has this car had the washer fluid line replaced? Its a known problem with the '06 Avant. The hose cracks, drips and shorts out the amp.
Fortunately when I had an Avant it happened when it was still under warranty.

kelisko

I had the exact same problem and thought it was because my battery was new. I was wrong. It kept happening.

After doing some research, I found out that cars equipped with Sirius satellite radio are prone to this. The Sirius module goes south at some point and stays on even when the car is stopped and locked. The Sirius module is in the trunk in the left compartment. It's installed vertically on the side of the MMI and Navigation systems units block. It's installed on the side facing the taillight. Try touching it. It should be warm if not burning hot.

I disconnected the Sirius module and parked the car for one week and my battery was fine. The issue returned when I plugged the Sirius module back.

The bad news is when the Sirius module is removed, the MMI does not work because this is part of the MOST loop. Removing the Sirius module creates a rupture in the loop and causes the MMI to fail.

People said a way to fix this is to remove the Sirius module, install an Audi Loopback Fibre optic Bridge in place and reinstall the MMI.

I ordered the Fibre Optic Bridge which should be delivered this week. I will try it out and let you know how it works.

Part number: 4E0973802

Nurke

Thats what happened in my wifes 3.2...got one of the loops..fixed mmi and forgot about it.. I never used sirius anyway...

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I removed the sat radio and Sat nav from the trunk awhile ago. I took apart these two optic connectors and shortcut the input from sat nav into the input of the amplifier. This left me with two extra pieces of fiber optic cable. The procedure was fairly easy. You need to push out a little blue wedge from the connector and it comes apart. Just be careful not to bend the cable too hard

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The washer line failed a year ago. I had a little plastic tarp covering the amp as a preventive measure. Since the washer line was originally fixed by the recall by the original owner or the car.
After the water broke, the tarp seems to do it's job and the amp was pretty clean. Just as precaution I took apart the amp and cleaned it with alcohol. Maybe it was not good enough. Will do more triiliage an this source of the issue and post the group.

Costasz

Is this a problem on the sedan as well? We have this battery drain issue but have not detected any washer leaks. Maybe it's subtle?

Nurke

mine is sedan and battery drain was due to bad serius module. In fact i had a battery drain and dead mmi..

Costasz

I ordered one of the clamp amp checkers. I need to check the Audi and my car (a bmw) both aging and having the same issue at the same time freaking german electronics.

kelisko

I removed the Sirius module and plugged the fiber optic bridge I ordered yesterday. The bridge looks big in pictures but it is very small and very light lol

The MMI came back on. I didn't reinstall the MMI but it works fine. The satellite radio option is just grayed out in the FM menu.

My battery level used to drop every morning. This morning it was at 100%. I will use the car a few more days, park it for a long time and report back again.