First time towing - no trailer lights. Am I doing something wrong? Factory tow package on a 2015 TDI. No brake controller (yet - on order). Hooked up the car trailer and zero lights. Works fine on the Suburban and Dakota. What am I missing? Some mode to enable in MMI (no air suspension here). Job for VAG-COM? Fuse to check?

 

I’m a newbie here too. I purchased and installed the proper 7-pin connector, plugged in the trailer and all lights worked fine.

 

You mean an adapter with built in resistors? I think that's going to be the solution.
https://www.etrailer.com/Trailer_Wir...ady/20142.html

 

This is the one I bought. It is what Audi would have sold you back in the day.

https://www.etrailer.com/Trailer-Wir...k/PK11893.html

 

I have something like that installed. So the trailer plug does go right in. Unless that one has some sort of resistors built into it, I think I need something additional.

 

So, two possibilities:
1 - For modern trailers with LED brake lights, those won't work unless you buy the 'LED' adapter...car is highly sensitive to current flow in the braking circuit, and just shuts it off, if not meeting parameters. The Curt adapter, which plugs into car's 7pin output, then outputs as a 4 or 5 pin trailer connector, is exactly what Audi will sell you for sooo much more than you can get it off Amazon, or buy it from a local U-haul towing center for. Don't be a sucker on the towing accessories. Originally, Audi didn't even include the 7pin, even though it was factory. You just the wire harness with a dust cover, waiting to connect to it, and it had to be bought separately, so that's often confusing to new owners, but the factory tow kit is the best, as it gives you the towing-specific, cooling system upgrades. On the 'Accessory' version of the tow Kit Audi dealers sell now, you get everything except for the factory cooling upgrades (includes larger, 600 watt, high output main radiator fan, a dedicated radiator shroud, and a higher capacity radiator. Depending on which model/engine you bought, you may already have the larger radiator or not...the TDIs have it. The base level gas engine did not get the high capacity radiator, etc. Be aware that once you plug-in the LED adapter (containing resistors to even out the power draw on the braking circuit, the car will 'think' you have a trailer connected if you leave the adapter plugged into the car's 7pin connector, which means all the car's systems linked to towing are still engaged in 'towing mode'...be sure to remove the LED adapter once you've dropped the trailer, or if you are troubleshooting a lighting issue; plug the trailer harness into LED adapter, then connect the adapter to the 7pin.

2 - The car should be factory programmed for towing, on cars equipped from the factory. Anyone adding the 'factory' tow kit has to program or get multiple control modules programmed to recognize and react to when the car is hooked to a trailer, etc. When adding towing to the Q7 via the OEM route, the towing module/lights controller/decoder also has to be added to the car when programming it for towing. You aren't done installing the OEM kit until the car has been programmed for it; it can be done via VCDS fairly easily. It is highly beneficial to use the OEM tow kit, as it allows integration with the car's existing safety systems.

 

This is good info.
I figured as much, but others might not realize this.
The car does have factory tow package, so I'm assuming the programming is correct and any increased cooling systems that come with tow package are still in place.
I will add the LED adapter to the trailer plug, and will definitely not leave it plugged in when the trailer is disconnected. I'm assuming that the adapter will also over ride the car's ability to monitor bulbs on the trailer; it will effectively be monitoring the presence of the resistors instead.

 

Update: That is the solution.

In hindsight, this is an easy issue, and very easy to solve. I'm just surprised there wasn't more posted about it. I just needed to buy a pigtail with built-in resistors to let the car know that the trailer was plugged in. Apparently the LED's on the trailer do not have the expected resistance expected by the car.

I guess Audi was trying to be too tricky with auto-sensing and bulb monitoring. Snacks of GM, if I'm honest.

Now waiting for a brake controller and extra pigtail for a spare.

 

Huh - great info, thank you. Did you end up getting this? https://www.etrailer.com/Trailer_Wir...ady/20142.html

I wonder if I'll need the same thing. All I did to test was a quick plug-in and confirmed my LED trailer lights worked. I haven't even pulled with it yet.

 

I have one of those on order, and I think it's going to be the best solution, but I also ordered and received this:

CURT 57003 LED-Compatible 7-Way RV Blade Vehicle-Side Trailer Wiring Adapter

from Amazon. Given the importance and possibility of someone "borrowing" it, I figured a spare was a good idea.