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2004 V10 Battery Draining Issue

19976 Views 19 Replies 8 Participants Last post by  barnardp

Being new to modern cars I took up the challenge and purchased a 2004 V10 Touareg and hgad it for about 12 days now. The day i picked it up the main battery was flat but by using the key it started first go. I test drove it a fortnight beforehand which was alright at the time.

The previous owner seemed to know nothing about keyless entry or keyless start. always used the key. He had it at the local VW dealer and an independant auto electrian for weeks to try and fix the clock resetting and the fuel averages resetting when starting the car. VW replaced the alternator which did not seem to fix the problem.

Since obtaining the car i charged up the main battery under the seat but it was beyond holding any charge. 2 days on a 10 amp charger and a load test brought it down past 5 volts. Replaced the battery with a new one and off i went. i do a fair bit of diring during the day and leaving around 7am and getting home 10pm with intermittent trips during the day started first time every time. Doing research and reading many things over batteries and drain i did upgrade the cd navigation from firmware 0629 to 0635

I came home early on a friday around 4pm and didnt work saturday. About 2pm saturday Tried to start the car keyless and all the electronics died as it cranked over. The battery was flat again. Swapped the battery with a smaller one i had from antoher car and put the big one on charge... which load tested fine on sunday morning.

The temporary battery was flat sunday morning. i then replaced the battery again with another full one and tested the vehicle according to the tsb on battery drain.

I bought the VCDS but still awaiting to obtain schematics for this vehicle

I checked every fuse 3 times on both sides of the dash and under the bonnet. I left an inline ammeter between the battery and notcsed the current being 2.5-2.9 Amps and occasionaly it would drop to about 0.1a for half a second but then back again to 2.5-2.9..for 3-10 second intervals.

I observed some fuses showing current on and off... notably Parking sensors, Tyre Pressure monitor system, Radio and a few others.

I then also heard a clicking noise of a relay every time this happened.

Finding the offending control box I found a box labelled "Bordnetzsteuergerat" 7L6 937 049 L which seemed to click and all these things turn on and off repeatedly. Unlocking the doors and ignition and the clicking stops.

First time with the VCDS VAG-COM software the only error I found on this control module was a 00907.... battery low which I would expect with the number of battery charges and swaps I did over the weekend

Watching the inputs that I could see on the VCDS I saw nothing unusual. I learnt I had heated mirrors that was on but that’s all!

The software won’t show you what the box is doing when the ignition is off so I couldn’t monitor the inputs.

Any ideas and what else this module controls or what it listens to when sleeping?

Or something else to look for?
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Confused - please give suggestions

This will be a long post - I apologise but am completely confused re V10 batteries.

Big question: if trunk battery is starting battery, then why have trouble starting due to possible inefficient, ie maybe stuffed, battery under passenger seat?
Let the story begin.

Presently have roughly 150 000km on the clock. At about 100 000km we went on an off road trip. I had connected a 12v cable for fridge directly to trunk battery. When I connected fridge just before departure, fridge showed low voltage. Too late to do anything, so I took along genset for fridge. Car started perfectly!

On our return, dealer replaced trunk battery with new OEM. No problems since, UNTIL went camping couple of weekends ago - remember, about 40 000km later. Had fridge connected and, after one night, the next morning vehicle,on pushing start button, engine went sort of "oomph", and all lights on dash went out. Then lights reappeared and I used the key to start (without anti clockwise turn). Car started ok, but gave "engine fault" and ESP "off" light on. After a couple of km's all settled back to normal.Ok, I thought, I drained the battery with fridge.

Next weekend out, I did not connect fridge to battery. When vehicle started 2 days later, exactly same issue as described above. Important to add- the tailgate and a door left open for long periods - ie, interior lights burning!

I then left vehicle in garage for 3 days - locked, nothing opened or used. Perfect start, no problems at all!

My theory is that the passenger seat battery is stuffed. That would explain the problems when interior lights are burning, they are using the (original) accessory battery.

My question is, if the rear (starter) battery is still ok - relatively new, remember - then why have a "starting" problem? I suspect that it is some "intelligent" electronics is playing between the two batteries.

And, before I get criticism (although most welcome), yes, I should have replaced both batteries at the same time. I also intend to replace battery under seat, but the sequels of events confuses me.

To end, no, I do not have voltage readings or any of those other technical stuff you guru's are going to ask for:)

I will appreciate the thoughts of the V10 "guru's".
Cheers, Werner
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Cheers, Drag, sounds spot on!
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