Yes, you'll more than likely need an additional wiring kit to charge the caravan battery and power the fridge (unless previous owner did it already). Check first, you may be lucky.
I took the easy route and got my local VW dealer to fit the auxiliary wiring kit for me. That way it's guaranteed. Cost about £170 to supply and fit if I remember correctly.

 

It would help if you told us what mark of Touareg you have, as the reply will vary from model to model.

There is a well known problem with T3s (New Touareg post 2009), in that VW do not fit the part of the wiring kit that provides the power to charge the caravan battery and power the fridge for factory fit bars. At present it is not known when they will overcome the problem and start fitting complete systems. This can be overcome if, on delivery, a knowledgeable dealer fits the missing loom freely available though the VW parts system. This indeed will happen next week when my T3 arrives.

For T1/T2 (1st Gen Touareg up to 2009) the fix is simple either a VW dealer or good towbar specialist can fit the appropriate loom. But after it is done it requires some VAGCOM intervention to tell the car that trailer wiring is present as the the system will know when a trailer is present and will automatically modify the software for the ABS, ESP and the alarm, which now operate if the trailer electric cable is disconnected. Also the rear fogs are disabled while the trailer is connected.

So you can see, it is a slightly complex system affecting the car's computers and Canbus, and probably worth having it done by a dealer, if only for the warranty it attracts.

 

Cheers chaps,

I think you have now confirmed what i suspected was the case.
I reckon i could quite easily sort it myself using a relay operated fused separate supply for both the caravan battery charger and the fridge supply, but i might just leave it. We havent really had any problems so far using the van without these supplies working. We always get on sites with hook-up so dont need to rely on the battery so much and a couple of freezer packs in the fridge do the job till we get there and get on the mains.
First trip out this year weekend before Easter (as Easter as well)... Looking forward to choking up the A roads again!

 

i had exactly the same problem when i bought my Treg. i took it to the dealer to let them sort it out. if i remember it was only about £70 i paid to have it all converted, with aditional pins for fridge and battery charging.

i also converted my caravan to a 13 pin socket, very straight forward job, much easier in my opinion than messing about with adaptors.

hope you get all sorted out.

 

Sorry to jump on the thread but I had a towbar and 13 pin electrics fitted to my T1 by a towbar company. They told me it would charge the caravan battery and run the fridge before they even looked at the vehicle. No mention of VAGCOM. How can I tell because the fridge works anyway if it's switched on with the caravan battery connected.

 

Taking the caravan alone, if the mains hook up is disconnected, then the Control part only of the fridge will be powered by the caravan battery. The fridge will not cool off the caravan 12 volt DC supply alone, (or any other 12volt supply for that matter when not connected to a correctly wired vehicle) it requires either the gas supply connected or mains electric for it to cool. The caravan 12 volts system always powers the control side of the fridge (either from the battery or PSU if switched on when mains hook up is connected).

Similarly, when connected to a correctly wired vehicle (without the engine running) the fridge control and some interior lights will be powered by the permanent 12v supply (pin 9 of 13 pin socket). If you have a Touareg without the extra auxiliary wiring fitted (not an uncommon event, especially with a brand new Touareg fresh from the factory with a factory fit towbar). Coincidentally, my brand new Treg is having the extra VW auxiliary wiring fitted today by the supplying dealer.

If you have a correctly wired 13 pin socket on your car, when you attach it to the caravan, without the engine running (doesn't matter if the ignition is on or off) the caravan controls will light up together some of the interior lights if they are switched on. Start the engine and when the car deems it safe (it prioritises the vehicle battery charging system) then 12volts will be supplied to power the fridge so that it will cool using the 12 volts vehicle supply on pins 10 and 11.

Any other type of wiring is dangerous and can damage the car's electrics and prevent it charging the battery (fitting a relay to allow the fridge supply when ignition on etc), it must be done via split charge relay sytem fitted by someone who knows what they are doing as ESP, ABS, Alarm and other safety systems are affected by connecting a trailer ESPECIALLY WITH ALL MODELS OF TOUAREG. A properly wired Touareg will sense the connection of a traier and make alterations to ABS and ESP to employ anti-sway, modify the alarm system so that it sounds if trailer disconnected and switch off the car rear fog light, there's also some bulb failure stuff going on.

Exactly the same circumstances exist if you have twin 7 pin sockets fitted.

So, connect the car, no ignition on or engine running, you should have fridge control lights on and some interior lights available. Start the engine and after a short while (you may have to raise rpm to say 1500 rpm), then the fridge should start cooling and the caravan battery should be charged.

If you have a reasonably modern Dometic fridge (most caravans seem to) then, when the fridge has only permanent 12 volts supplied for the control circuit (either from car or caravan battery) then you will see a flashing blue LED on the control panel. As soon as any other cooling supply is available (gas, mains electric or vehicle 12 volts) and cooling the fridge (you will have to select this by the appropriate button) then the LED will stop flashing.

HTH.

 

the whole point of the auxillary electric pins on the cars 13 pin euro socket or the grey 12s socket is that when the caravan is connected to the car, the caravan battery and the fridge are kept going via the cars alternator via a split charge circuit to save the caravan battery from being drained due to the fridge using the battery power.

the fridge should work when the caravan master switch is turned on, but the caravan systems should be isolated and the car system kick in a when the caravan is connected to the car.

hope this helps a bit.

the Treg is a complicated car and sometimes its better to bite the bullit and spend a few quid at the dealers to get things done right first time.

 

top explanation Fil!!!! i am sure that will help.

 

Agreed. Spoken like a truly knowledgeable caravan/VW salesperson

I for one hadn't realised the level of complexity of the interface wiring between van and car.

 

That was a good explanation fil. Thanks

 

you can maybe understand my theory of spend a few quid at the dealers now...