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2012 touareg tdi sport w/nav
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Discussion Starter #1
My 2112 is not charging my trailer battery.
Checked the fuses on passenger side of dash (25,15,15 and15 amp)
All other funtions work.
I did find the brake control harness and installed a brake control. It works too just no battery charging.
 

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I had the same. There is a separate fuse for just that, which was blown. Can’t remember the fuse number... Maybe worth checking the fuses once more.
 

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Check fuses 6,7,8,13 on the right side fuse panel. They are 15a, 25a, 25a, 15a respectively, and supply the towing recognition module.

Fuse 6 and 13 (15a) are most likely for the running lights, and fuse 7 and 8 (25a) are most likely for the brake output and charge.
 

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2012 touareg tdi sport w/nav
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Discussion Starter #4
Great hope thats it. I am thinking about installing a self reseting breaker to avoid this problem.
 

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If you keep burning out the fuse then there is probably something wrong somewhere... most likely the trailer wiring or perhaps a high current load that exceeds the rating of the fuse and more importantly the wiring.

What do you tow?
 

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2012 touareg tdi sport w/nav
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Discussion Starter #6
So far I havent found any burnt out fuses. I have a small travel trailer with 2 group 27 deep cycle batterys. I run them pretty dead dry camping. When i figure out why the Touareg doesn't charge I am thinking of using a self reseting breaker on the trailer to protect the Touareg.
 

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Check the voltage on the center pin of the 7 pin. It should read about 12V vs a clean grounding point.

Also check the ground between vehicle and trailer when only the 7 pin is connected. Trailers frequently experience unnoticed grounding issues because they ground through the trailer ball rather than a corroded or faulty ground wire.

Also corroded 7 pin connector or socket causes all sorts of issues. I use liquid tin or terminal cleaner to clean them up.

The 7 pin socket should be clean as it has a weather resistant cover. If not you can buy a new one on Amazon for $20z made by Pollak I think.
 

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2014 Audi Q7 TDI
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I've got a full battery monitoring system, the OEM trailer wiring is only capable of providing like 5A max.. with a dual deep cycle battery bank thats like pissing in the ocean, not an adequate charge current.. would take like 24h of solid driving to make a dent in the charge on em.. and with lead batteries, at max charge rate your still looking at >8h of charging needed to bring em back to full from a deep cycle.. max charge rate for 100AH of FLA is at least 15A, more w/AGM, with two thats at least 30A charger needed to charge it as fast as it'll let you (~8h), any less than that is just going to increase charge time dramatically.

You also have to account for any loads running while driving, got a 3A fridge going? well then your down to 2A of charging current.. I could spend 8h stuck in traffic on Memorial day and get home to find the battery has hardly charged at all.. Its also nearly impossible to fully charge a trailer battery over that much wiring, the voltage drop is significant enough that you will only get it partially recharged because its not seeing full voltage after 30ft of 14awg.

now I've got a 325W solar panel fixed to the roof, so on a nice sunny day I'm getting >20A charge current driving.. enough that I can both charge up my bank, and run a crockpot to cook a meal while on the road.
 

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Check the voltage on the center pin of the 7 pin. It should read about 12V vs a clean grounding point.
centre pin is reverse lights, no? Charge should be at the 1 o’clock position when looking at the socket, and ground at 7 o’clock. At least that’s how my past 3 Touaregs have been.
 

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Last I looked there are two possible pin outs for 7 pins. They interchange reverse and 12V + .... I think....

But otherwise you are correct.

Maybe the trailer is wired wrong??
 

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2012 touareg tdi sport w/nav
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Discussion Starter #11
I've got a full battery monitoring system, the OEM trailer wiring is only capable of providing like 5A max.. with a dual deep cycle battery bank thats like pissing in the ocean, not an adequate charge current.. would take like 24h of solid driving to make a dent in the charge on em.. and with lead batteries, at max charge rate your still looking at >8h of charging needed to bring em back to full from a deep cycle.. max charge rate for 100AH of FLA is at least 15A, more w/AGM, with two thats at least 30A charger needed to charge it as fast as it'll let you (~8h), any less than that is just going to increase charge time dramatically.

You also have to account for any loads running while driving, got a 3A fridge going? well then your down to 2A of charging current.. I could spend 8h stuck in traffic on Memorial day and get home to find the battery has hardly charged at all.. Its also nearly impossible to fully charge a trailer battery over that much wiring, the voltage drop is significant enough that you will only get it partially recharged because its not seeing full voltage after 30ft of 14awg.

now I've got a 325W solar panel fixed to the roof, so on a nice sunny day I'm getting >20A charge current driving.. enough that I can both charge up my bank, and run a crockpot to cook a meal while on the road.
I gave up on the touareg charging and just bought a 100w solar system for the trailer. Works fine in Arizona. I will figure something else out in washington state when i go back
 

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I agree, with a travel trailer vehicle relying on vehicle charging is a losing game, even if you added a high amp DC-DC charger and upgraded wiring to support it are you still gonna drive 8h+ every few days to refill your batteries? I go out for weeks on end and usually am just fine w/solar, sometimes it dont cut it.. winter shadows or thick forest, and for that I got a genset to recharge.. I can run that all day long on idle no problem.. a honda 1000W would do fine if you dont have any aircon to run, Ive got a 2200W

I tried it w/my Golf, ran a heavy gauge wire all the way to trailer to charge it.. only if I was doing >600m every few days would it refill, otherwise it was a losing game hopping down the coast a couple hundred miles at a time.. now my trailer has a LFP battery, that thing will take 50A and go from empty to full in 2.5h.. I could work with that driving every few days w/the trailer on most trips, but damn it'd cost alot of money and be alot of effort to get 50A of DC from the vehicle back to the trailer.. only feasible IMO for onboard house batteries like truck campers/rv's and then you have to worry about the LFP overloading your alternator because most are not designed to output that kinda load for hours on end.

The 7 Pin 12V Charging Line is a trickle charge designed to keep an emergency break-away battery topped off, on a Camper the best you can hope for is it'll maintain the battery while traveling so you show up at camp w/same charge you left with despite the fridge running along the way..
 
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