A6 Allroad Electrical disaster, is this the end?

[mhobson]

Hello,

Audi A6 Allroad 11/2006 3.0 tdi 233 bhp.

I had some issues with the electric tailgate which Crasher gave some advice about but things have gone from bad to worse.

I drove the car on Saturday, no issues.

Yesterday morning I tried to start it, totally dead, battery had 2.25v. Battery was new 12/2021, Varta silver 110ah. Because the battery is in the boot I tried to jump start it using the connections under the bonnet, no chance. I tried charging it using an 8 amp charger via those connections. The charger gauge was going wild from top to bottom and the reset button kept popping out.

I climbed through the rear seats and disconnected the battery, charged it to 12.3v, reconnected it, started the car and left it running for a while then turned it off. Next morning dead again, 3.3v.

With the battery charged again I put a meter between the clamp and positive terminal and the battery was losing about 91 milliamps which is too much but I have no idea where.

Now when the car is running the screen shows radio not installed, What is happening?

Can anyone suggest what is going on? Maybe it is time to sell the car but who would buy it, I have owned it for 12 years and we have become a bit acquainted.

Positive suggestions greatly appreciated.

[smiffypr]

91 milliamps (0.091 Amps) is not enough to flatten a good, fully charged battery overnight. But you battery wasn't fully charged anyway at 12.3 volts. A 110ah battery on a 5 amp charger is going to take at least 22 hours. On top of that, flattening the battery to that extent twice will probably have killed the battery. I would try to recharge your battery fully or borrow a good battery, disconnect any accessories you have connected or plugged in, and try again.

[mhobson]

91 milliamps (0.091 Amps) is not enough to flatten a good, fully charged battery overnight. But you battery wasn't fully charged anyway at 12.3 volts. A 110ah battery on a 5 amp charger is going to take at least 22 hours. On top of that, flattening the battery to that extent twice will probably have killed the battery. I would try to recharge your battery fully or borrow a good battery, disconnect any accessories you have connected or plugged in, and try again.

Thank you for the reply. I do have a brand new unused battery, but I am worried about killing that. The time before last that I drove the car I had loud cracking sounds coming from the speakers, but the radio was not turned on, I couldn't deal with the noise, returned home and used my wife's car, next time I drove the car that issue did not arise, I wonder if there is a connection especially as now, when the car is running the screen says "Radio not installed", very odd. I am well out of my comfort zone.

[smiffypr]

I would suggest charging the new battery, put that in the car, don't start it. Check the radio. If that is now okay, you then know that the old battery was causing the radio problems. Then I would leave your meter connected across the battery measuring volts where you can see it through the window, lock the car and check the voltage every hour or so. That way you will see if the voltage is going down fast and be able to disconnect the battery before it is flattened. From fully charged, my battery drops as much as 0.15 volt between hour 1 and hour 12, but then, around 0.02-0.04 volts every day. If it is going down fast, you can then investigate the current draw. Mine is about 10 mA. 100mA will flatten the battery so the car won't start over a few weeks. To drain the battery, which was charged enough to start the car, maybe 50%, overnight, would need a 5 amp drain, but if the battery was operating at 20% capacity and 50% charged, then 1 amp would kill it overnight. If everything seems okay (radio okay and battery voltage staying up), then try starting the car with the voltmeter still connected. Mine gets up to 14.75V when charging hard. If yours get much more than that, it could be that the battery has been killed by being overcharged, in which case I would turn the engine off and investigate the overcharging.
The other test you should do is to totally charge the old battery (until the charger says it's charged or the current has got down to nothing) then leave it disconnected and monitor the voltage to see if it is going flat on it's own.

[mhobson]

Thank you again. I will try charging the new battery as you suggested, but following your previous suggestion I have taken the old battery out and am charging it until tomorrow morning. It was difficult because as it has an electrical tailgate I had to climb through the back of the car, lift it up and out of a rear door, I already have a knackered back and am likely to be having a second lumbar surgery shortly, and it is a very heavy battery, I am also worried about dropping it or the new one when putting it back in the car. Tomorrow my initial plan is to put the old battery in place, connect the negative and with keys out and all doors shut to see what drain is occurring between the positive and the positive clamp. The last time I had the engine running with this battery the voltage was 14.4v. I have never charged a new battery, I will see what voltage is showing on that. I may have to revert to taking out individual fuses and see if one circuit is responsible for the drain, but it is very difficult with the battery in the back and a locked tailgate.

[Crasher]

I give up with modern batteries, they are hopeless; I haven't experienced so many flat batteries since the days of air cooled and a 28amp dynamo! I was working on a Golf 2 16v this morning, newish Yuasa 3000, started the engine, turned it off, went to start it again and click, flat as a witches ****!

[Whippy53]

But what's the reason? Poor manufacturing? Poor materials? Poor QC? Must be summat.

[smiffypr]

Why not connect the other battery to the charging/jump start points under the bonnet in order to work the tailgate?
As for checking the drain, if you leave the tailgate open, will the car not shut down after a while? I think mine took about 20 minutes with doors and tailgate open. I did the taking fuses out while looking at the current drain. (My problem was that I had left the OBD thing plugged in which became obvious when it got dark!).
I'm fortunate to have a drive to park on so I can run an extension lead out of a house window and charge the battery with it still in the car.

[Crasher]

But what's the reason? Poor manufacturing? Poor materials? Poor QC? Must be summat.

I don't know, certainly lockdown was hard on them.

[mhobson]

Battery was on charge overnight, disconnected it from the charger, let it settle for a half hour, showed 12.41v, after another 2 hours it was still above 12.3 and has shown no signs of dropping. I am ging to leave it connected overnight and see what it is like tomorrow. When I tried to start the car or charge it from the connections under the bonnet when the initial fault occurred it was hopeless and weird things seemed to be going on, speakers crackling, ignition turning on an off. I still have the issue "Radio not installed" I have no idea what to do about that, I put the Audi CDROM in the machine and followed setup instructions but no change. Today the car started easily, I wonder if the issues I have had with the electrical tailgate could have caused my problems, it still won't open more than 8 inches without assistance, the motors must use quite a bit of power. I suspect the in the not too distant future my car that I have loved for 12 years may have to find a new owner, I just don't have the finances to keep it going.

[mhobson]

After some hours the disconnected battery was not dropping voltage. After reconnecting 3 hours later it was down to 9.5v. At that time the loss was 99ma but I do not know what it might have been had the battery been up to charge. I do not think the battery is the fault, I think that there is a parasitic drain that I have not located. To prove it I may recharge the battery and put it on my wife's A4 overnight and see what happens. I still have the "Battery not installed" message coming up on the MMA, don't know what I can do about that. Tried updating using the Audi CDROM, no help.

[smiffypr]

Are you sure the drain is 99mA? not .99A (990 mA). When I had a 90-110mA drain the battery went flat over a period of many days. I'm not saying it is just the battery, but I think you ought to check it further, and that is what you are doing by trying it another car. Alternatively you could get it checked by a garage, they will have a device which puts a large load on the battery and they should give you a figure for the internal resistance of the battery, very useful if you try to get it replaced under warranty.

[mhobson]

Are you sure the drain is 99mA? not .99A (990 mA). When I had a 90-110mA drain the battery went flat over a period of many days. I'm not saying it is just the battery, but I think you ought to check it further, and that is what you are doing by trying it another car. Alternatively you could get it checked by a garage, they will have a device which puts a large load on the battery and they should give you a figure for the internal resistance of the battery, very useful if you try to get it replaced under warranty.

Thanks for your reply. You don't have to guess that I am not a born electrician, but I agree that 99ma should not drop the voltage that quickly, I tested on Ma and A ranges, the amp range showed about .1 amp. The battery was on the other car overnight, it did drop a little, from 12.4 to 12.35 but not enough to cause the big issue. After watching videos I am going to follow suggestions, opening all doors and locking them, then going through all of the fuses one by one and checking each for an excessive draw. Looking at recent issues with the car, I think that it might have something to do with the radio, I use it very rarely but a few days before the big voltage drop, I went out in the car and big cracking noises were coming out of the speakers, I had to go home and change vehicles it was so distracting, next time I drove the car that did not happen, but the first time I tried to charge the battery in situ that occasional crackling started again. Now the MMS says "Battery not installed". The other electrical issue is the electric tailgate, it will only open a few inches on its own and has to be helped up, but it closes on its own fine. I have to wait for fine weather, I do not have a garage wide enough to have the doors wide open while checking it out. If I find the culprit I will post a message. Regards, Michael

[smiffypr]

Before you start (good luck with the weather!) double check your meter. Ideally test it with a known current e.g. a bulb. My multi-meter gives stupid readings when it's own battery gets low. Your tests suggest a significant current drain from your car but 99mA and 0.1A show that it's not you miss-reading the meter. I think you did say that you are disconnecting the battery and connecting the meter to the battery lead and the battery, so all the current is going via the meter.

[mhobson]

Before you start (good luck with the weather!) double check your meter. Ideally test it with a known current e.g. a bulb. My multi-meter gives stupid readings when it's own battery gets low. Your tests suggest a significant current drain from your car but 99mA and 0.1A show that it's not you miss-reading the meter. I think you did say that you are disconnecting the battery and connecting the meter to the battery lead and the battery, so all the current is going via the meter.

It is true that I come to this site for good suggestions, and again you have not let me down. I have changed the meter, chalk and cheese, when I started measuring the amperage the volts on the battery were 12.37, first of all the amperage started at over 9 amps and was jumping up and down as I could hear relays or circuits turning on and off, the lowest it dropped to was 1.9 amps and after about 5 minutes it had stabilised to an average loss of about 5.5 amps, the battery voltage had dropped to 11.71 volts. That is quite a loss. I will have to recharge the battery and wait for good weather when I am not working and go through the circuits, but I suppose had the fault been on a 5 amp fuse it would have blown, so more likely on a higher amperage circuit. I still do not understand the "Radio not installed" message I would have expected the radio to be on a low amperage circuit.

[smiffypr]

That's a good result, lucky that I had problems with a meter in recent days so it was fresh in my mind. You are now in a good position to determine what is drawing that current (when time and weather permit). Regarding the radio, bear in mind that canbus vehicles can shut down power to something if it seems faulty, so the power to the radio might be being shut off deliberately (but in error) by one of the many controllers. So you could ignore the radio problem for now, find the power drain and isolate it, then worry if the radio problem is still there.

[swalker]

Good way to check a DMM battery health, measure a voltage - easy on cars 12V, swap the leads around, if the battery is stating to impact the results it wont be -12V.
this reminds me of working on the UR, fuse 12 got the nickname Stephen, something to do with a rugby song?

also if you have a good meter you can check the voltage across the fuse - saves you from having to pull it - ohms law, (V=I X R) voltage current and resistance are all related so the fuse has a small resistance so there wil be a voltage drop across it.
for example your 9 amp drain could show up as 0.9V 9x0.1(resistance of fuse), and the 1.9 amp drain could show up as 190mv 1.9x0.1.
Guessing the 0.1, but it should be there or there about and a constant. There are a few videos on YT, south main auto did one a years or 2 back on checking a fuse without pulling it. It would save the risk of waking the car up and having to wait 15 minutes between fuse pulls!!

good luck

[mhobson]

Gone from bad to worse. Started trying all the fuses for drain, all the fuses I was trying showed no or little current flowing. Tried in the boot, and the panels inside the front doors. I noticed that in the videos I had been watching that they had been checking the amperage between the negative pole and clamp and I had been using the positive post and clamp. on the positive side it had been showing about 5.5 amps, but when I put the meter on the negative side it shot up to 25 plus amps and blew the fuse in the meter and copious smoke emanated from the meter. Looks like I will have to take it to Audi, I may have to apply for a loan.

[smiffypr]

Different values of fuse are going to have a different resistance, so it would get complicated. Suerly the way to avoid waking things up is to unplug one fuse at a time while monitoring the battery drain, but leave the fuses out until you are finished.

[smiffypr]

The current at the two battery terminals won't be different, at the same time. Something must have decided to take more current just when you connected the meter. The way to avoid this blowing up your meter is to connect a jump lead between the battery and the battery clamp (meter also connected in such a way that it will stay connected when the jump lead is removed.), then once the locks have stopped clunking and the hazard light switch illumination has gone off, disconnect the jump lead. (I would guess that someone had put the wrong fuse in the meter if it blew up before the fuse blew.) Back to the fuses, are you saying that you took out all the fuses and it was still showing 5.5 amps? I don't know what else might be connected direct to the battery, but the ones that always used to be are the starter, the alternator, the ignition (the sparks) and the ABS. So if you can get a new meter and the motivation to continue, I would suggest that the next thing to disconnect is the alternator.

[mhobson]

Gone from bad to worse. Started trying all the fuses for drain, all the fuses I was trying showed no or little current flowing. Tried in the boot, and the panels inside the front doors. I noticed that in the videos I had been watching that they had been checking the amperage between the negative pole and clamp and I had been using the positive post and clamp. on the positive side it had been showing about 5.5 amps, but when I put the meter on the negative side it shot up to 25 plus amps and blew the fuse in the meter and copious smoke emanated from the meter. Looks like I will have to take it to Audi, I may have to apply for a loan.


So eventually I think I have found the problem, it seems that a zener diode in the alternator has gone rogue, doing a diode test, current is flowing in both directions, so I will order a new alternator, it looks a bit of a fiddle to change, very little room to work. I wonder if there is a chance that when replaced the CAN BUS issues might resolve, cross fingers.

[Crasher]

They are evil buggers to do.

[mhobson]

So after a lot of expense and heartache I finally found the issue with the car. Apparently the alternator was not the issue, despite testing it and finding current flowing in both directions when I expected the zener diodes would restrict it to just one direction. I took the car to a vehicle electronics specialist who worked on the car for 14 hours. Apparently there are three different electronic systems managed by a controller and the controller was turning systems on and off constantly when nothing was turned on and the key was not in the ignition and it was losing a constant 6 amps. It also damaged the webasto diesel heater system which I have only used once in 12 years and the technician had to buy a bypass cable from Audi to stop the drain there, but it also blew the radio control box in the boot 4F0035541H, There seem to be a lot for sale second hand and I will have a go at buying one, but I wonder if I will be able to just connect it or will it need to be reprogrammed.

[Crasher]

It will be VIN Component Protected and require ODIS and GEKO security clearance to unlock it.

[mhobson]

It will be VIN Component Protected and require ODIS and GEKO security clearance to unlock it.

Ah, so that is what the man meant, thanks for clearing that up.

[mhobson]

It will be VIN Component Protected and require ODIS and GEKO security clearance to unlock it.

How is that coding achieved? Can it be done by VCDS or what system manages it?

[mhobson]

How is that coding achieved? Can it be done by VCDS or what system manages it?

OK I looked that up, very complicated, leave it to the specialist.