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Discussion Starter · #1 ·
Hi all, I'm a new Audi driver with a 2013 Q5 and I've had the towbar retro fitted by Audi plus the addtional fridge & battery charging kit.

The problem I have is that I think a fuse has blown that runs the fridge via a relay. There is a red wire that runs from the RH side of the boot to the front of the car but I can't trace it any further than just below the driver's side fuse box. It could be behind this but just wanted to ask if anyone knows for sure where it's fused before I dig any deeper?
 

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Hard to say exactly where they've plugged it in but my guess would be it's going into the rear of one of the spare fuse sockets on the right hand bank of fuses.


The fuse box unclips and you can move it so that you can see into the back of the holders, the yellow wire in this photo is an extra one that I fitted to get a switched 12v.



If they have done it this way there will probably be a fairly big fuse, 20A or so, in one of the blanks in the first photo which you could check.

The other way they could have done it is by using a piggy back or break out fuse which will be a lot easier to spot as the new wire will be in front of the fuses.

Also, might seem like a daft question, have you connected up your caravan to check if it's working?

The reason I ask is that I tried to test my fridge & charger wiring was complete with a multi meter on the pins in the socket but that didn't work, the car seems to know when a trailer is attached and doesn't power them up until one is connected.

I confirmed that my caravan battery was charging by putting the multi meter over the caravan battery and then monitoring it whilst the engine was started. Took about 10 seconds for the caravan's 12v controller to click and then the readings started to increase so all was good.

If it's not working Audi should sort you out but you might not get a quick answer about the fuse because it's not unknown for them to sub contract the towbar work out to independent specialists.
 

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Discussion Starter · #3 ·
Thanks SteveMcB, yes I've connected it up to the van and it does (or did) run the fridge & charge the battery. I'll check out behind the fuses now.
 

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Discussion Starter · #4 ·
Yes it did go into the black fuse block but as a yellow wire - sneeks changed it from red to yellow wire as it entered the side panel!
Fridge is now working except that it's on all the time the ignition is on not just when the engine's running; the ignition sense is tapped into the dynamic steering fuse.

Still have a problem with the battery charging/ATC pin not having any volts - do you know where this is powered from SteveMcB
 

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Yes it did go into the black fuse block but as a yellow wire - sneeks changed it from red to yellow wire as it entered the side panel!
Fridge is now working except that it's on all the time the ignition is on not just when the engine's running; the ignition sense is tapped into the dynamic steering fuse.

Still have a problem with the battery charging/ATC pin not having any volts - do you know where this is powered from SteveMcB
Quite difficult to say without having a look at how they've done it. Surprised they've tapped off the steering though, I would have expected pros to put in an additional fused circuit (takes 10 minutes max) or at least use one of the spare slots.

Did you find a blown fuse?

Could be the relay is sticking or a wire has come out, may explain the blown fuse, it'll probably be somewhere in the boot near or in the fusebox, that's where most of the stuff for the factory towbar is.

Your ATC should run off pin 9 ( I think - not got ATC myself) which should be permanent live. They might have connected straight onto the battery because it's nearby (and easiest to get to) so probably worth having a look in there as well for an additional wire with inline fuse, the other option would be the left bank of driver side fuses but I'm guessing you'd already have spotted that wire.

Because there are so many different ways to wire stuff up it can be quite difficult to figure out how someone else has done it.

It's probably worth checking everything because you'll want to find out why the fuse has blown in the first place.

If the work was done recently I'd take it back to Audi and tell them to sort it and also mention that you're not happy with them tapping off the steering and want it done properly, ie with a repair wire.

Personally I think Audi should have added a repair wire to the left bank and right bank (costs about £3 in parts) to give you OME permanent and switched supplies each protected by it's own fuse in the fuse box. There's probably options in the boot fusebox as well but I haven't been in there yet.



 

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Discussion Starter · #6 ·
Car going back to Audi dealer and the caravan back to Swift dealer. Turns out the ATC on the van doesn't initialise at all now, even with the old car connected, but is does charge the battery!
 

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Your ATC's memory is probably full and needing reset, there's a high likelihood that the dodgy power supply from the car has caused this so you might want to consider just how much info you give the caravan dealer
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They'll clear it with a laptop but there's a way to do it yourself involving leaving the car hooked up for a few hours.

I think I'm right is saying that all Q5s have towbar prep, I'm not exactly sure what this is but would have thought that it would make plugging in the Audi harness pretty straightforward with no need for odd bits of wire piggy backed off a steering fuse?

If I were you I'd double check they have used a genuine Audi harness ( they are very expensive compared to the generic £20 jobs ) but they are needed for the car to 'know' when it's towing and to activate all of the safety features. It also needs coded into the car with VCDS.

You should get an additional green light in the dash when indicating and the reversing camera/display changes with no beeping.
 

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Discussion Starter · #8 ·
OK I'll try leaving the old car hooked up for a few hours.

I do get the indication of a trailer connected when reversing with the Audi and a green indicator on the dash when indicating so the car definitely knows when the van's hitched up.
 

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Discussion Starter · #9 ·
Good news - the ATC has started working again. I can hear it initialise correctly when plugged on to car's socket, which also means I now have a permanent 12V supply on pin 9. Proved this by being able to select car battery in the van to run lights etc.. However when I start the engine the habitation relay disconnects the van's lights, as it should, but it still doen't charge the van's leisure battery
. Sounds like a blown fuse between the habitaion relay and the battery but I can't find any blown fuses in the van at all.
 

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Discussion Starter · #10 ·
Well, I found the the fuses for the incoming permanent 12V supply and the fridge supply and also the charging fuse - they were all good, but now everything works as it should
. Must have reset something when pulling these fuses but now that I have fridge running and battery charging from the car I'm a happy bunny.
 

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Well, I found the the fuses for the incoming permanent 12V supply and the fridge supply and also the charging fuse - they were all good, but now everything works as it should
. Must have reset something when pulling these fuses but now that I have fridge running and battery charging from the car I'm a happy bunny.
Good news. Did you get the towbar wiring checked? ATC is apparently very sensitive when it comes to the power supply, if it's not completely stable it will log faults which fill the memory and cause it to shut down.
 

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Discussion Starter · #12 ·
No, as it was with my old car that it locked up when I was checking the caravan's fridge & battery charging - i think it was too many quick reconnections of the 13pin socket. The old car has since been sold.
 
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