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First of all, you need to use a test light. Not a meter. Something that draws 12V. The system needs to sense that something is connected to become activated.
Secondly, in order to activate the system you need to hold the test light to pins 1 & 4 for about 2 seconds. (or any ground and pin 4) You will then see your test light come on. Do the same thing with the hazard lights on and your test light will start blinking. Test both left and right side. (pins 5 & 6)
I prefer to use a ground found elsewhere as not to accidentally short anything out. just sayin'
Thanks for this! I'll give it a shot next time I'm out in the garage.
Another question I had: Do you know if the Aux +12V circuit in the Q5 has its own current limiter? Forgive me if my understanding is weak but here's my though process:
If I connect Aux +12V direct to the trailer battery, if there is no circuitry to limit the current then the trailer battery will draw as much amperage as it can, possibly overloading the wire running back the trailer.
My initial plan was to use a DC-DC charge controller on the trailer but if the Audi has its own current limiting circuit that would remove the need for me to use the charge controller.
Pin 4 carries very low amperage and is heavily throttled down by the trailer control unit. Barely enough to charge a battery. In my experience it maintains the trailer battery at best. If I'm doing multiple days in the sticks I bring along my Honda 2200 and plug the trailer directly into that and let the trailer's built-in charger/converter do its thing or use a generator and a battery charger together.
The 12V plug on the 2200 is crap and very unreliable. Hence me not using that option.
Blue and red trailer brake connection at the rear.
Hi, I'm new here. I have a 2013 Q7 that came with an aftermarket hitch and no trailer wiring. I need to wire up for 7-pin trailer lights and brakes and I think I have the hardware I need (I'll be using a Tekonsha proportional controller) and the know-how with respect to the lights. It's the brakes that are confounding. I have seen a couple of useful videos on accessing the factory brake controller harness at the front of the vehicle under the dash. However information about the other end of that harness at the rear of the vehicle has been VERY hard to find. Dudealicious posted a series of pictures of his Q5 project (I'm hoping it translates to my Q7), one of which appears to show the trailer brake wiring harness at the rear of the vehicle (the other end of what starts under the dash?). It looks like the area inside the rear right wheel well. Am I on the right track here?
You're in the right area. Completely remove the plastic in the passenger side trunk area. There's a 2-pin plug wrapped in black fabric tape with identical wire colors to the 2-pin plug under the dash. Just keep poking around.
8R0971541C is not the correct harness. I purchased this previously. The connector would not fit the control module. Additionally the trailer end is 13pin euro
Hello,
European here about to make this retrofit aswell but can't seem to find any info for that market so maybe you guys can help me out
For now I have only obtained the 8K0907383E. I will get a universal fixed hitch but the issue is like you're aware the harness.. I found this one on a german site, it has the right module connector and the price is okay:
It's missing the 2pin red/blue connector but from what I have read that is for the braking control (correct?) - which we don't need in Europe? And regarding this 3pin connector that's apparently for the trailer lock indicator light according to the website support. And I won't be needing that either since I'm mounting a fixed towbar I guess?
Thanks!
You are correct. 2-pin is for brake control.
The D module has the 3rd socket which operates that fancy "hidden hitch release" mechanism. As you mentioned, yours will be fixed which will make that 3rd plug unnecessary.
As long as the black 12-pin plug on the harness and the 16-pin plug, which was factory installed, all line up with your control module you should be good to go.
You are correct. 2-pin is for brake control.
The D module has the 3rd socket which operates that fancy "hidden hitch release" mechanism. As you mentioned, yours will be fixed which will make that 3rd plug unnecessary.
As long as the black 12-pin plug on the harness and the 16-pin plug, which was factory installed, all line up with your control module you should be good to go.
so blue goes into the module, it has 3 wires that go to the small plug which is the light, 17 pin goes into the oem tow harness, and the black 16 pin connects to the module
Does anyone have the part number for this harness or know where I can buy one I need to buy one of these for my Q5.
Thanks
12-06-2021, 04:28 PM
