Audi A4 B7 Convertible 13 Pin Socket Electrics

[a_goodman]

Hi

Last year I bought a 2007 Audi A4 convertible with original Audi detachable towbar and electrics fitted. The lighting connections all work as expected, but the additional caravan related pins don't seem to fit the standard wiring convention at all, meaning my caravan fridge isn't powered when driving.

So far I've found:
Pin 9 - ignition switched live. 0v with ignition off, 12v with ignition on, 14v with engine running.
Pin 13 - earth
Pin 10,11,12 - no terminal in socket

The standard specifies that pin 9 should be a permanent, unswitched live, suitable for powering the caravan internal lighting etc off with the engine switched off. Pin 10 should be a switched live that's only 12v when the engine is running, suitable for powering the caravan fridge.

The standard (as I understand it) also specifies that the permanent live can be switched by a relay in the caravan, using pin 10 as a signal, to charge the caravan battery.

I'm trying to decide on the best way to get my fridge powered. It'd be nice to have the battery charging too, but not v important to me. The easiest thing would be to change the caravan plug wiring to run the fridge off pin 9. As this is switched on my car it would be safe and not let me discharge the car battery when the engine's not running. I'd obviously have to be careful if using it with a different car though.

Has anyone come across this strange Audi wiring before, and do you know the current rating of the supply to pin 9? (I've read about pin 10,11,12 being empty, but not pin 9 being switched).

Has anyone got a better suggestion that doesn't mean replacing the whole Audi wired socket?

Thanks
Andy

[adrian41uk]

I've been having fun retro fitting a towbar on my 2008 A3 and have also come across some strange things....

Are your towing electrics genuine Audi? I have discovered that the genuine Audi electrics only cater for road lighting & don't cater for the 'auxiliary circuits' which supply permanent & switch 12V for a caravan.

I also discovered that the Westfalia electrics kit (which can also be supplied under a genuine Audi part number) had a wiring error that resulted in the switched 12V ('terminal 15' in audi speak) being connected to pin 9 instead of pin 10. This sounds similar to what you are seeing. (I bought my electrics kit via a 'well known auction site'. It came in an audi box & contained the genuine audi trailer ECU module. All the wiring had both Audi & Westfalia logos on it)

I did contact Westfalia and they did offer to supply me with the crimp pins to add the missing contacts into the 13 way socket (having pointed out that they are missing 'by design') so that might be a way forward for you. If you can get hold of the correct release tool you might be able to remove the contact from the pin 9 in the 13way socket & insert it into pin 10 where it belongs. On my kit, the switched 12V is fused at 15A by fuse No 46.

Pin 12 is the trailer detection pin. I've never seen this implemented so I wouldn't worry too much about that.

Adding the perm 12V ('terminal 30' in audi speak) could be a little more tricky. Ideally you want to take the feed from the main fuse box under the bonnet & fuse it at 15 or 20A. The thicker the wire the better.

Hope this helps!

Adrian

[a_goodman]

Very interesting. My 13 pin socket has the Audi logo on the cover, so I assumed was genuine Audi, but it's sounding like it might be the westfalia kit under the Audi part no. Does yours have the Audi symbol on the socket cover?

I've not seen any of the wiring or trailer ECU module yet as haven't removed any of the trim, so not sure about logos on that.

I'll try fuse 46 tomorrow and see if that kills my pin9 feed. The fridge draws about 8.5 amps, so 15 would be fine.

I'll also have a look at moving pin9 to 10 in the socket tomorrow - that hadn't occurred to me for some reason and would avoid having to make the caravan non standard.

Think I'll live without the permanent feed for now. Battery charging would be nice, but I've managed the last few years without it in my last car and never been bothered by it. Looking forward to a working fridge though!

Thanks for your advice,
Andy

[adrian41uk]

Yes, it has the Audi logo on the 13 pin socket cover. And on various tape labels on the parts of the wiring harness. You may out more when you access the ECU (for the A3, its behind the right hand side boot trim. Theres a great 'How to' thread on here detailing what to do to remove the trim & warnings about the 'secret' screw).

I did find, during my research stage of trying to find which towbar to fit, that the genuine towbar that would be factory or dealer fitted would be a Westfalia. In fact, the pictures that are shown in the cars manual match exactly my setup. I've since noticed the Westfalia logo on other things so conclude that they are an official supplier).

For my install there are four fuses which serve the towing system. Fuse 46 supplies the switched 12V to the trailer socket (and nothing else). Fuses 44 & 45 feed the trailer lighting circuits - one supports all the near side lights, the other supports all the off-side lights (and nothing else). Fuse 2 supplies (amongst other things) the switch 12V to the ECU so it knows when the engine is running.

My kit has 12 pins brought out from the trailer socket (pin 12 is empty). Most connect directly to the trailer ECU, the others go to two 3 pin inline connectors. One of these carries the switched 12V & two earth connections - this routed to the front fuse box. The second 3 pin carries the perm 12V & its earth. This is left open in the boot. The kit doesn't contain a mating other half for this (it isn't supposed to, apparently) and I'm now hunting down the correct mating connector to implement this.

I don't see any reason why just implementing the switched 12V should give problems, obviously you cant charge the caravan battery or operate the internal lights from the towcar but I think the fridge should still work.

Adrian

[a_goodman]

Well I've had a successful day and got the fridge working.

This morning I took the 13 pin socket on the car apart. Fairly easy with some patience and determination. At one stage I had to release 6 clips at the same time, so one by one wedged 4 of them open using crimp spade terminals before holding the last 2 open and pulling the socket apart. After removing one more piece of the assembly, all of the crimp terminals were hanging free on their wires. It was the quite easy to then move crimp 9 to position 10 to give me a switched live supply in the normal position.

I had a look at my fuses and just have one related to the towing assembly - fuse 27, rated at 30 amps. Unfortunately, I forgot to check what I lose when I pull it out. My fuse box only goes up to number 40 though so obviously different to the A3.

I noticed the socket cover also has the VW logo on it. I didn't notice a westfalia one though.

I ran the fridge/freezer off the car for about 40 minutes with about 8.5 amps drawn and it definitely started to freeze.

I'd still like to add the permanent 12v supply for charging sometime but am not looking forward to having to remove all of the trim to feed it through, so will see. I've not yet come across a guide to removing the A4 convertible boot trim. Did westfalia give you a part number for the missing crimp terminals when you contacted them?

Andy

[adrian41uk]

Glad you managed to move the pins across.... at least that was easyish.

I would have expected more than one fuse for the trailer .... its usual to split the electrics NSR & OSR. If you tell me the variant code/engine code/gearbox code & year of reg of your A4 I should be able to access the wiring diagrams and tell you what I find.

Westfalia didn't give me a part number for the pins .... below is a excerpt from their reply. I contacted them using the 'contact us' form on their UK website (their UK operation is in Stafford).

'Unfortunately the charging line circuit (pins 10 & 11) was not part of the original Audi request for the product, therefore we have not added the pins and wires to enable you to use the charging line extension easily.

However, if you really need it – you can add the pins into the socket (I can provide crimp pins) you can run the wires into the boot insulating carefully (I cannot supply wires & insulating material), and then use the combined extension kit 300025300113.
300025300113 is the extension to give both auxiliary feeds; charging line (pins 10 & 11) and the permanent (pins 9 & 13)."

[a_goodman]

The codes (if I've picked out what you need from the service book sticker correctly) are:

Variant: 8HE 07L
Year of manufacture: 02-03-4117 (2007??)
Engine: ASB-
Gearbox: JAX-
The reg is 07, delivered march 07. It's the 3.0 V6 diesel engine with auto gearbox.

I'd be interested to know what you find. The fuse box cover showed another fuse related to towing, but it was empty and shown as vacant in the manual.

[adrian41uk]

I have managed to access the schematic for your car.

There are two fuses which relate to the towing system. Fuse 27 (30A) supplies perm 12V to the towing ECU & hence feeds all the road lights. This does not supply the switched 12V trailer socket. This seems to come from fuse 77, also 30A. (Is the wire you had on pin 9 a black/yellow wire?) The drawings seem to suggest that fuse 77 is not located in the fusebox but is attached to the 4 way relay carrier which is part of the on board power control unit. On the A4 I think this is located behind the lower dash panel, drivers side.

If you send me a pm with your email, I'll send you a pdf of the part schematics I have.

Adrian.

PS. What part of Notts? I'm very close to M1 J25.

[EddyP]

If you're still working on this, on the Westfalia website you can download the original wiring instructions and it mentions the extra bits for the charging/fridge wiring. Might help you out?

I've done mine in the last couple of weeks, but from scratch, no dedicated kit, in the end I used a couple of spare slots in the dash fusebox and ran it down the inside trim and round into the boot.