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Discussion Starter · #1 ·
Not another I hear you cry, so let me start from the beginning. I have two brand new batteries , but this problem has been with me for a few years but it is getting wose
I start the car at home no problems drive for about an hour with the voltmeter reading about 13 volts. Stop the car and when I try and restart engine turns over to about one second then stops. Sometimes it will start after a few attempts but not always. If not if needs a jump start. It happened today and when I got to My
destination . I turned off the engine and then it restarted immediately no problems. It's all very intermittent and sometimes I can go days without it happening again. Anyone any Clues??
 

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Your voltmeter should live on 14.
13 on the meter will not cut the mustard. When my generator failed the needle danced around a lot which I took to mean a bad regulator. Not sure what would cause a steady 13. Whatever that is is your problem.
 

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Not another I hear you cry, so let me start from the beginning. I have two brand new batteries , but this problem has been with me for a few years but it is getting wose
I start the car at home no problems drive for about an hour with the voltmeter reading about 13 volts. Stop the car and when I try and restart engine turns over to about one second then stops. Sometimes it will start after a few attempts but not always. If not if needs a jump start. It happened today and when I got to My
destination . I turned off the engine and then it restarted immediately no problems. It's all very intermittent and sometimes I can go days without it happening again. Anyone any Clues??
G'day from Down Under - I had the same issue on my 2009 R50 - would not start when at normal operating temp after a very short stop for refuel for instance. My auto electrician examined this and after quite a bit of trouble shooting, found severe arcing on the plate below the positive pole under the bonnet. He disconnected the batteries, removed all connections on this plate and polished everything up - re-assembled - no fault since. I hope it proves to be a long term fix. Cheers, Dan
 

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Discussion Starter · #4 ·
Thanks Dan, good to hear from down under, I was thinking perhaps a dodgy relay contact so that may fall in with your fix, but following I gibsons post I measured the voltage before starting from cold and I had 12.8 rear and 12.5 front and it started perfectly. Next step is to measure voltage if and when it happens again. At least that might point to charging or connection problem
 

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Yes, we are talking about the importance of your system voltage as indicated by the voltmeter in the instrument panel. Over the years the word has been it must be steady as a rock on 14V.
 

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Thanks Dan, good to hear from down under, I was thinking perhaps a dodgy relay contact so that may fall in with your fix, but following I gibsons post I measured the voltage before starting from cold and I had 12.8 rear and 12.5 front and it started perfectly. Next step is to measure voltage if and when it happens again. At least that might point to charging or connection problem
Very good - please keep us posted on this - others down under have the same issue and there my be several causes - mine seems to be OK since the sparky did that clean up :)
 

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Discussion Starter · #7 ·
Good to hear yours is ok now. We're away for few days so using the R50 every day for a change. Typically since the issue on the first day its been perfect but I'm determined to get a permanent fix as I love the car and dont want to change it. I'll keep you posted
 

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Discussion Starter · #9 ·
Well it happened again. Been driving previous day started every time no problems. Next day press starter clunk and nothing measured voltage at rear 12.56 pressed start button again and instantly started..
Today after long drive home rear battery 12.54 front battery 12.31 under Bonnet +ive post 12.32
So I'm going to tackle the plate under the post under Bonnet to see if that helps. But why is the post under Bonnet same voltage as the front battery when it's supposed to be the rear battery which starts the car??
 

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The interaction of the two batteries is complicated. Somewhere out there is a VAG Self Study Program (SSP) describing the system. About all I remember is there is a relay connecting and disconnecting the two batteries..
 

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Well it happened again. Been driving previous day started every time no problems. Next day press starter clunk and nothing measured voltage at rear 12.56 pressed start button again and instantly started..
Today after long drive home rear battery 12.54 front battery 12.31 under Bonnet +ive post 12.32
So I'm going to tackle the plate under the post under Bonnet to see if that helps. But why is the post under Bonnet same voltage as the front battery when it's supposed to be the rear battery which starts the car??
G'Day mate - many of us down under have come to the conclusion that there is an error in some documentation about these two battery set ups - I for one and many others have concluded that the front battery under the seat is the starter battery, not the rear one. This makes sense when you think logically about it - why when you add a second battery would you go to the expense and re-engineering to change all the original wiring and set up for engine starting?

Anyway, good luck with correcting your problem - mine does seem to be holding up since this work was done! Cheers, Dan
 

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Go to the following to locate the SSP on the V10 Touareg Electrical system - particularly around starting system, relays etc.



As Dan above has noted (and Drag previously as well), I as well as others believe the battery under the passenger seat is the PRIMARY battery for starting the car (just as it is for those 7L Touaregs with only one battery). The rear battery (which is a lesser rated battery than the front under the seat battery) can be included in the electrical starting process (Anticlockwise turn of the key) should the use of the front battery (a clockwise turn of the battery) not get the engine started.

Have a read of SS298 - free download.
 
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