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2005 mk1 Touareg V10 tdi in black
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Discussion Starter #1
Mk1 Treg V10 tdi with intermittent low voltage/random fault codes that may be wiring harness related.

Have finally got access to rhe cabin floor wiring harnessses. First splice I came to was both corroded and the wires had also separated from one another.

View attachment 238177

Have twisted them together so there's no confusion when the soldering starts tomorrow.

Also found a lone wolf with an oxidised end. Its a red wire with a yellow stripe. There's no other half to it along the remainder of the harness so am guessing that it may have come out of this splice which has three separate wires in it already?

View attachment 238178

View attachment 238179

If anyone could point me in right direction it would be appreciated.
 

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2005 mk1 Touareg V10 tdi in black
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Discussion Starter #3
Well, have got Tasha back together after re-doing the splices that were oxidised.

Cleared the error codes and five remain but its early days and a good run might improve things. The volt meter is now holding at about 12.5 V on the gauge. Not exactly accurate I know. It used to hold at a solid 14.5 but when the battery issues started the needle steadily dropped to below 11 V.

Does anyone's voltmeter regularly read 12.5 V without issue?
 

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Something is not right at 12.5V. Measure and report your battery voltages with a handheld meter. Need to know.

1. What the battery reads after sitting overnight before starting engine.
2. What the battery reads when the engine is running.
3. What the battery reads after you just turned off the engine. Let engine run at least 10 minutes or more before you do this one.

The v10 has two batteries. It makes it fun.

You might just need new batteries.

At this point, it is a good idea to start inspecting and cleaning the ground points. It is almost certain that the metal ground strap that goes from the engine to the chassis is probably needing replacement, or if you are lucky just a good cleaning.
 

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2005 mk1 Touareg V10 tdi in black
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Discussion Starter #5
Thanks for the tips Nicky.

It does sound like fun. Almost as much fun as ripping the interior out and inspecting the wiring looms lol

Have got 3 of my Grandchildren staying over today/tonight so will make a start early tomorrow if they sleep in.

One of the batteries is new and both have been out and on charge during the interior job so both went back in yesterday fully charged.

Will do the battery and engine ground checks and report back asap.

Thanks.
 

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Thanks for the tips Nicky.

It does sound like fun. Almost as much fun as ripping the interior out and inspecting the wiring looms lol

Have got 3 of my Grandchildren staying over today/tonight so will make a start early tomorrow if they sleep in.

One of the batteries is new and both have been out and on charge during the interior job so both went back in yesterday fully charged.

Will do the battery and engine ground checks and report back asap.

Thanks.
Each battery controls a different section of management, so they BOTH need to be 100% in order for the systems to work properly
 

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2005 mk1 Touareg V10 tdi in black
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Discussion Starter #7 (Edited)
Houston,

we have a problem!

238210


238211


As per the above from Nicky here are the results...

Rear battery:

Pre-start
707 CCA 12.63V 3.83 milli Ohms

while engine idling (10 mins)
698 CCA 12.59V 3.84 milli Ohms

immediately after shut off
695 CCA 12.59V 3.86 milli Ohms

Front battery:

Pre-start
346 CCA 11.97V 6.47 milli Ohms

while engine idling (10 mins)
12 CCA 11.22V 145.1 milli Ohms

immediately after shut off
182 CCA 11.6V 10.45 milli Ohms

Both batteries were fully charged when I put them back in 48 hours ago.

Have checked the negative cable from the front battery to the ground point and it looks clean with no obvious damage or oxidation.

238212


Can't see the engine ground strap in the engine bay so haven't checked that yet.

Definitely something wrong up front but am electrically challenged so not a clue what to do next.

Any advice is appreciated.
 

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It's not Houston. I hope Madrid can help ;-)
I used to own a VW Phaeton with a dual battery set up too. It had a large electric junction on the plenum chamber, next to the engine bay. I am aware that some owners reported low voltage issues caused by corroded/damaged wires connected to that junction.
In case your V10 had a similar junction, it would be worth checking it.

Gabriel
 

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I had a car with a similar problem. fortunately I had another car I could just swap modules and relays with. Also I had a plethora of parts from a few cars I dismantled. in my case I was able to figure out the issues but on advice of others I parted ways with the car when everything was fixed.

unfortunately these cars are getting close to 20 years old and if there are wiring issues present they will continue. Unless you bought the car new and did all the work or know what was touched it may be time to consider moving on...

Cars from hot or wet areas seem to be most prone to wiring issues. Mine was from Arazona and moved to Texas. When you did a side by side with my Maryland car you can see the deterioration of the harnesses.
 

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Discussion Starter #11
Gabriel,

Mucho gusto, my friend :)

I will check that junction when the rain stops.
 

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Discussion Starter #12

Hi Blownvette,

Thanks for the info. I've only had her since December and really want to keep her so am resigned to repairing/ replacing what needs attention to keep this old girl on the road.
 

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Discussion Starter #13
Bonjour mon ami,

Please see the pictures below:

Pre-start with ignition on

238215


Immediately after start up

238216


For the first minute of idling there is a new ticking sound from under the steering wheel area. While it is ticking the voltmeter needle fluctuates between 11v and 12v.

When the ticking stops the needle rests as below

238217
 

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Discussion Starter #15
The rear battery had a full charge when I took it out. Am presuming if its holding voltage then the alternator is working. Also, the headlights are still very bright.
 

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The rear is for starting only I think. You will not see a big drop unless you start the engine several times. There should be a way to make sure the alternator is working properly. One of them is seeing 14v on the dash gauge when engine is running.


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Discussion Starter #17
It has shown 14.5v on the dash until the front battery is too low to power the consumer electrics.

238218


Since getting the Treg tin December the rear battery hasn't been charged other than from the vehicle's system and it had a full charge when I took it out last week when the wiring splices in the footwells was checked.
 

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Hola amigo,
I have been having a look at th SSP 298, that is the one that deals with te touareg 7l electric system, and the electrical junction that I mentioned earlier seems to be under the left front seat, next to the battery, not at the plenum chamber.
In any case you can have a look at a weath of information here:


Best of luck.

Gabriel
 
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