Hey, guys, I'm looking for some guidance on where to go with a trailer hitch wiring problem on my 2014 S7. The background is that I want a trailer hitch to tow a small sailboat on occasion for my daughter. The boat weighs a couple of hundred pounds and the trailer itself is less than 200 pounds, so I will not be towing a big rig or anything like that.

Since Audi doesn't offer a hitch for the S7 in the USA as a standard option, I bought an aftermarket hitch designed for the A7 from Westfalia in Germany and had it installed. This tow bar is a beautiful piece of engineering that mounts behind the bumper cover and is completely invisible from the rear until you insert a removable gooseneck tow ball from underneath the bumper valence. The hitch hardware went right in - no custom drilling was required and it all bolts in cleanly. I even got the modified S7 bumper valence which allows access to the hitch from the bottom, which is a standard Audi part in Germany.

My problem is that the shop which mechanically installed the hardware was clueless on hooking up the wiring, despite the instructions from Westfalia. They sent it out to a guy that allegedly knew how to plug into the car's wiring harness, and he couldn't get the signals (for brake lights, blinkers, and running lights) to work. I believe that after plugging the hitch wiring into the car where indicated in the instructions, you have to program the car's computer with settings that activate the hitch signals. If I take it to the dealer, they will just tell me that a trailer hitch is not offered on the S7 in this country, and they won't touch it (note that the MMI has a user selectable suspension setting for towing, so this is clearly something that was contemplated somewhere).

Does anyone have any suggestions for a place or person that knows how to troubleshoot a wiring/computer issue like this in the New York City area? Thanks in advance.

 

Well, here's the update if anyone is interested in installing an OEM Westfalia trailer hitch on your S7. After experiencing the electrical connection problems I described above, I took mine to the Audi dealership to get help on the coding of the car's electronics to recognize the hitch when a trailer is plugged in. The dealer agreed to do the work, but then in the process discovered that their standard online system of recoding did not work. The dealer then contacted some tech resource at Audi USA and learned that he could, in theory, do a manual entry of the proper settings, but Audi would not release the coding specs to a US dealer since the S7 was not registered with the US DOT as having a trailer hitch option (!). The good news is they could hook up the trailer directional light, running and brake light wires, but they had to leave the plug into the CAN-bus disconnected. As a result, the several adjustments to the car's operation that should occur when towing won't happen; i.e. turning off rear camera, turning off rear parking sensor warning, adjusting suspension (there may also be changes to the ACC and active braking systems). The dealer also pointed out that even if they were allowed to manually make the coding changes, they would be overwritten each time the car was in for service, and would have to be reset to avoid fault indications. As long as the trailer lights worked, I agreed to live without the full integrated connection, since I will be towing a trailer or using a rear bike rack very infrequently, and will even less frequently be backing up with the trailer/bike rack attached (I can manually change the suspension setting for towing since it's an available option in MMI - in fact, the existence of this towing option in MMI was one reason I did not expect to have any problem with the installation). I suppose I could get the coding settings somehow and try to do the manual update away from the dealer, but its not worth the trouble to me. However, if anyone is successful in doing so, I would be interested to hear how it went.

 

THX for the info. Too bad it's such a PITA for Audi NA to cooperate with a customer that spends $90K on one of their products.