Suspicious Battery Drain

[JasperMatthews]

Good Morning/Evening/Night Audi Owners!

I've owned my Audi S3 for around a year now and have had this issue nagging at my side for around the whole time and are still unable to solve it. I've noticed one other thread with a similar issue, however with no solution there either, just wondering whether there are any other people with similar issues.

When charged, my 2009 Audi S3 8P starts every time, however, after a single day or two of non-use the car either struggles to start or doesn't start at all. That's the issue. Now for the list of things I've tried:

• Taken the car to an auto-electrician to examine the fuse box, and investigate any possible power drains - unfortunately found nothing.
• We've replaced the battery 3 times, different brands each time, with the same issue.
• Replaced the alternator entirely and then fully charged the battery before running it. Lasted around 2 weeks, before I wasn't able to drive it for a few days and it's not dead again.
• Checked to ensure there are no lights on inside or out of the car when I leave it overnight.

Just wondering whether anyone has had any experience with the above issue and whether you were able to get any solutions? I love the car so much but I'm getting a little tired of worrying after leaving it for a day of non-starting, whether or not it's going to start or not.

Thank you,

Jasper

[Magnet]

Hello Jasper,

As your thread heading suggests, there must be a parasitic drain on a circuit which is drawing current when the car is ‘shut down’.i.e. about 30 seconds after the car is locked up. 

Apologies if this is resisting the bleeding obvious, but you simply need to find out which is the offending circuit, then what within that circuit is actually causing the drain. 

It would sound as if you would benefit from the services of another auto electrician - one who can monitor the current (pardon the pun) amps drain, before removing each fuse in turn until that drain disappears. Presto! - that’s the offending circuit. 

Kind regards,

Gareth. 

p.s. Normal ‘at rest’ drain should be around 50mA, so you are looking for drains greater than that. 

[JasperMatthews]

Hey Gareth,

Thanks for your quick reply! From what the original auto-electrician mentioned, that's what he did. They monitored it post the 5amp shutdown period (30seconds post-locking the car) and once that period passed, the drains that were there, were within standard tolerances - so they shouldn't be draining anything more than what the car would need to reserve to start back up again.

However, if there's another approach you've heard of, we'd definitely be open to suggestions to try them!

Cheers,

Jasper

[Magnet]

OK Jasper,

As I see it the logic will follow this path:- 

They are saying that once the car has fully shut down, the measured drain was within ‘standard tolerance’. Can you confirm with them what that measurement actually was in mA? 

So let’s say it was acceptable at the time they monitored it after the car had fully shut down. So it was OK then. 

If the battery is subsequently draining - which it must be - then something must be ’waking up’ later, and staying awake, so the car’s drain would need monitoring over an extended period to confirm or refute that the drain is taking place. 

Puts me in mind of talking with a very prestigious marque technician who was trying to solve a repeated parasitic drain. Found the offending circuit - sorted the cause, and left the meter connected while he had a rewarding cup of tea. Returned to find the drain had returned! 

Kind regards,

Gareth. 

 

[JasperMatthews]

It was a 0.5mA 50mA drain or thereabouts. Wasn't big enough to worry about they noted - so I assume it was within tolerance.

So now I feel like I need to go through and do my own check on the car. I've got a multi-meter, so I might see if I can see any more draws coming from the battery either using the AMP scale or mA scale to see if there's any odd smaller ones too.

We have a suspicion that it's happening intermittently and that the auto-electrician managed to miss it occurring somehow - so hopefully we get it!

Will keep you updated on this Gareth. Thanks a lot for your help mate!

Cheers,

Jasper

[Magnet]

Hello Jasper, 

A consistent 50mA is fine, but as I said - consistent is the operative word. 

Not sure how you are going to continuously monitor this over an extended period without ‘timed-referenced-back’ equipment - sleepless nights and boring days! 

Kind regards,

Gareth. 

[Coogs]

I had similar problem on my 2004 B6 S4. Turned out to be faulty radio head unit internals. Try removing the fuse for the radio - preferably while monitoring current (drain) on the battery with a multimeter. 

[JasperMatthews]

Definitely got some boring days coming up, but thankfully should only take 2-3 days max, so I should just be able to monitor it over the weekend!

I've noticed a while back that the steering wheel light has lit up a feint Amber colour, and among further research people are indicating it could be a failing instrument cluster/binnacle - so maybe that's an issue?

Anyway, I'll do some further investigation and let you know how I go @Magnet

--------------------------------

@Coogs definitely something I'll be looking into also.

Will be checking almost all the fuses, as process of elimination is key.

Thanks all!

Will report back.

Jasper

[JasperMatthews]

@Magnet @Coogs 

UPDATE:

So, we ended up doing a fuse pulling test the other day to try and find the offending circuit, and ended up figuring out what was draining the battery! Here's what we did:

1. We linked the multi-metre (set to 10amp mode) to the battery to try and detect the drain. We noticed the standard cooldown drain once the car has been locked, which settles after a few minutes to around 300mA - which is obviously still high!

2. After finding the 300mA drain, we began fuse pulling taking out the fuses one by one in the engine bay fuse compartment, and eventually found that fuse F20 (Navigation and Phone), once pulled, reduced the drain down to about 10mA, which is far better! We did some research and found that it was linking to the old telephone mount in the car, which a feature available to Europe at the time since phone usage while driving was still legal in some countries, namely Germany, but was removed when imported to Australia by law. So we guessed by disconnecting the cable (for which was found by removing the rear ash tray behind the centre console), that it would remove the drain - however, this didn't actually fix the issue for whatever reason.

3. After disconnecting the old phone mount cable, we actually just decided to remove the fuse as a whole, disconnecting that circuit and trying to figure out what might not work (we figured the RNS-E's navigation might be impaired once this fuse was removed after looking at the wiring diagram), but interestingly, everything still functioned perfectly fine! So we've just settled with keeping that fuse removed for now, and the drain has stopped without any noted issues stemming from it!

Hopefully this solves some other people's problems too!

Thanks for the help guys,

Jasper

[Steve Q]

Glad you got this sorted Jasper 🙂