End of my teather!! Battery Drain

Sp3no82

Registered User
I am having a nightmare with my A4 B7 Avant S-line at the moment, if I leave the car for 2 days or more the battery is completely flat!! Its to the point now where I carry a power pack in the boot to jump start the car, and I'm having to use it regularly.
Today I decided to look into this, I got a multimeter and tested the alternator was charging, +14v when running, so happy with that, battery is less than 6months old so chances are that ok so it was time to investigate further.
I disconnected the negative lead and read the Amp usage across the circuit when the car is sat with nothing on and I'm getting 3A which seems way too much but I'm no expert, I went through the process of pulling fuses one by one until the Amps dropped, I pulled the fuse for the radio and hey presto the reading dropped to 0.95A which still seems high? I pull the rest of the fuses and it never dropped below 0.95A
I have a RNS-E plus and yanked it out the dash and sure enough when I pulled the plug out the back it dropped from 3A to 0.95A
It clear the problem is with the RNS-E unit, can this be fixed, is this common issue? as a temporary measure I have pulled the fuse for the radio and I'm going to see how the car is over the next week. If I drive it every day its usually ok but if left for that extra day then the battery is completely dead.
Please help me know what to do, I'm thinking about chopping this car in as it been nothing but trouble for me :-(
 

carlcall

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You'll find that the RNS-e stays live for about 30 minutes once the key is taken out.....I had this problem a while back and it was due to the battery having a dead cell in it. As long as I caught it before it went below a certain threshold I was fine. Got a replacement battery under warranty and all is fine now.....I can have the RNS-e on for hours and it starts fine.

Get an automotive place to test the battery.....but unplug the RNS-e so they don't say it's down to the height current drain.


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Sp3no82

Registered User
Thanks for the reply, my battery is under 12 months old so its worth taking it back for a replacement if it could be faulty. I have left the fuse out for the Radio, will get a new battery and see how it goes. IM wondering if I should unplug the sounder for the alarm too just in case that's the reason for it still pulling 0.95A
 

carlcall

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In all honesty that isn't that much of a drain but I'm sure it should be closer to .6amps


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Sturat

Registered User
This may have nothing to do with it but I had a problem with my avant, my fans came on for no apparent reason which drained battery. Ended up being water in the bottom of the ECU housing, The relays were sitting in water. This did however throw up loads of fault codes. Have you checked for fault codes?
 

344bigal

Registered User
My B7 Avant had a similar issue, when I bought it the RNS-e didn't stay on or switch on without the ignition on. I found out that the fuse was missing so I replaced it and it all worked but the battery would go dead every day or so. Pull the fuse for the constant feed to the stereo and voila, battery stays charged.
I keep meaning to look into it further but just haven't got round to it yet as all it means is switching the stereo on manually.

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Bulbul68

Registered User
Sp3no8,
Hi there, did you get to the bottom of the battery drain issue?
My wife’s B7 Cabriolet started doing this a couple of years ago so I replaced the battery and all seemed fine for 3 years then the problem started to come back. I cheacked the drain with an amp meter and found 3.9 amp drain which dropped to 2.9 after a minute. This was with the doors locked and alarm on. I removed the radio 20amp fuse and repeated the locking procedure. This time I got 950 milliamps dropping to 50 milliamps (0.050 amps) after 1 minute so I’m pretty sure it’s the RNSe, the question is why?
 

carlcall

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@Bulbul68 after a bit of digging it looks like the RNSe semi powers up when you unlock the car so it boots up faster.

I eventually got my Kenwood back off the Mrs when she got a new car.....never had the fault since and it's been over 6 months now and I've had the doors open with the puddle lights on for hours whilst doing jobs on the car. It was a right PITA when you'd been working for a few hours and you had to jump start it.
 

Bulbul68

Registered User
@Bulbul68 after a bit of digging it looks like the RNSe semi powers up when you unlock the car so it boots up faster.

I eventually got my Kenwood back off the Mrs when she got a new car.....never had the fault since and it's been over 6 months now and I've had the doors open with the puddle lights on for hours whilst doing jobs on the car. It was a right PITA when you'd been working for a few hours and you had to jump start it.
So can the RNSe be fixed?
 

carlcall

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VCDS Map User
Just one of those things I think you may have to live with.....mines an RNSe Mkll as I upgraded it from the original Mkl and it was just the same.

I was meant to look into whether you could change the settings in VCDS but never got around to it as I got my old stereo back off the Mrs.

It sounds much better also....yes it was the top of the range Kenwood about 5 years ago and cost me a fortune as it had DTS 5.1 surround sound and all sorts of other things to enhance the sound like speaker set up etc. But after listening to the RNSe for so long I thought it sounded good.....until I swapped it. Even a cheaper stereo would sound better IMHO.

Basically you have two choices, see if it can be recoded to stop it turning on when the doors are unlocked and reduce the time it’s live for or go for an aftermarket head unit.

If you do go the aftermarket route get a surround like the one I have that doesn’t require the stereo bezel surround and makes it look more OEM.

CT23AU06.jpg



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I'm Just Rob.

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Carl, when you say stereo bezel which piece are you referring too.
 

carlcall

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Fingers crossed for you @Bulbul68

Carl, when you say stereo bezel which piece are you referring too.

The part in between the screen and the new fascia Rob....if I have time later today I'll take a picture of mine. Bearing in mind I couldn't find my bezel as I didn't need it when I fitted it into the Mrs' old car as I fitted it into a custom fascia I made. ****** Mk1 Focus's wasn't a single or double din but more like a 1 & 3/4 din.
 

desertstorm

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Unusual to have a faulty Bosch/ Varta battery but of course not impossible. You can get side tracked with the cars when pulling fuses etc and still seeing what appears to be high current loads as the modules have to go into a low current sleep mode which sometimes takes a few minutes after the car is locked. Current then should be around the 50mA mark as stated earlier.
RNSE issues though are a common source of flat batteries.
 

Bulbul68

Registered User
I’m now thinking of running the 20 amp radio live through a relay which is powered with acc power, what do you think?
 

blackpool1974

Member
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Would you lose your settings every time you switched off ?

I think RNSE doesnt make you put the code in if it loses power which it will everytime you switch off, but the radio presets, GPS and also radio settings might default to factory settings everytime you switch on ?
 

I'm Just Rob.

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Dog hairs in the car...that's just normal for my old bus too its the price ones pay's for having a dog with a coat that just gets every where. ..my GSD has a coat worse than a yak...…..lol

Anway, I like those facias carl, thinking I need to invest in one aswell…..where from chap.
 

carlcall

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Its a CT23AU06 from Connects2 CLICKY.....but you need to order a couple of bolts to hold it in place as they don't come with the kit. I'll try and root out the thread and length you need.

Also the clips on the side need to be cut on mine as it comes to light that there are two types of housings that hold the OEM stereos in place. Mine had a Black Plastic type but there is also an Aluminium type that the clips lock in to.

Connects2 told me they'd never heard of the plastic type before.....but if you don't cut them off if they are not needed you will struggle to push the stereo into the cage and you will struggle even more to get it out.

Once bolted in place it won't move and doesn't make any funny noises.
 

I'm Just Rob.

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Thanks for that Carl, top man as usual..:icon thumright:
 

I'm Just Rob.

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mine has metal everything …..
 

carlcall

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Yours will hold itself in place but the screws make it more secure.

I can't find my order for the screws but M4 x 20mm Flanged button head bolts rings a bell with me.
 

p-rossi

Registered User
I realise the date of the posts here but I've had the battery drain as well. I have a 56 plate A4 B7, Quattro, BUL, S-Line, Special Edition. I believe it had RNSE in it from factory (inc phone prep but not BT), however, when I bought the car it had a no-name media/ICE unit fitted (seller told me the original RNSE was duff & put in this substitute). I put in RNSE (genuine Mk II, 193G, H/W 05, F/W at 0650), which caused a battery drain overnight, around 10 hours with car locked. I measured a draw of 2.5 - 3Amps with a clamp meter & so I did what others have done on numerous posts & pulled fuses 1 at a time. My timing on pulling fuses to monitor current draw was rubbish so I didn't get to see it stop. I wasn't sure if pulling a particular fuse would wake something else up causing false measurements, so probably not really a sound method of investigation.

Turns out, after an investigation by a non-OEM auto electrician, it's RNSE causing the infotainment CAN bus network to wake up & drain the battery. As I understand it (reading the Bentley manual) these platforms don't have a dedicated CAN module & it's the instrument cluster that hosts the CAN gateway.

So, the sequence of events was that, after locking the car, the modules would eventually go to sleep after around 15-20 mins & only the alarm system was running (about 60mA). After that, the RNSE was waking up & triggering the CAN infotainment bus in the instrument cluster but considering the current draw, it might have triggered the drivetrain & convenience bus as well, although, I didn't go into whether these buses were being activated or analyse the data on it. Monitoring the routine, all modules went to sleep after a certain amount of time-out (15-20 mins) & then RNSE repeated the routine & woke the modules up again after about 10-15 mins.

Does anyone know if the CAN electronics on RNSE is a plug in module/daughter board that be replaced or reflashed? If not, I'm not sure what to do about it as I can't find anyone who will look at this kind of fault. Most repairs are screens, buttons & disc drives, etc. Any ideas what could be causing CAN on RNSE to come alive every 10 mins - incorrect coding or wiring? When RNSE wakes up, would monitoring the data on the CAN Hi & Low lines tell me what it's trying to do or what message it's sending out? Could it be the gateway itself waking up just because RNSE is connected?
 

Kingofsmiths

Registered User
Having the same battery drain issue.
Only thing is I have the Audi Concert double din head unit although with BOSE and factory Bluetooth phone prep.
So never read all this RNS stuff and just assumed it was a bad battery (this could still prove to be the case).
So a day go I had a RNS-e fitted by a VAG specialist near me - this was so I could have Bluetooth music and telephone calls. During the install he ran vcds and couldn't find the Bluetooth module, we checked, checked and checked again even put the old Concert head unit in, still no sign of the Bluetooth module. Not having time to tear the car apart we left it with the RNS unit in.
Morning came completely dead battery. After today googling a faulty Bluetooth module can cause this !! And makes sense it the vcds couldn't talk to it.
So fuses (phone and radio) out tonight to see what happens?
Have a new Bluetooth module fully coded on the way so will fit that when arrives.
 

madstaff

Registered User
Hi Allan, the battery was fitted new Jan 2021 and my (your) car was sat unused for over a month until you made contact again and had no problem starting so I would be very surprised if it was a battery fault.
I never experienced a flat battery in all my years of ownership.
I must admit I didn't really use the Bluetooth function, but I did on the odd occasion so I know it must have had it fitted, I can only assume the BT module has recently developed a fault.
 

Kingofsmiths

Registered User
Hi Dave, cars been faultless mate, and love it.
It's probably the last two weeks it's struggled to start i.e needs more cranking or has a flat battery (twice) This was all with the Concert head unit.
Bluetooth worked fine when we all set it up when I collected the car but never really used it after and just thought it lost connection, so not paid much attention.
Pulled the radio and telephone fuses last night and started ok but again took a little longer this morning.
I have the new Bluetooth module but won't be able to fit it till next week now.
...... I'll try that then maybe try a new battery although I find it hard to believe it's that but you never know. Can be a mine field looking for answers on here or Google so might try to keep it simple.
Thank you for the reply Dave.
I'll post on here if things improve etc
 
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