How to Tow a Trailer with US 7-Way Using a 2014 Audi A6 with Euro 7-Way  

I have an Audi A6 with a European trailer module that terminates in a European style 7 pin connecter. I tow a trailer with a standard US 7 blade connector. I first purchased part #118710 thinking that it did the work of combining the European Left, Right, and Brake lights into the US Left+Brake, and Right+Brake. I realized that it didnt, so I added a couple diodes from the Brake to Left and Brake to Right within this adapter. This gave me most of the desired functionality, but of course when the brake was applied at the same time the turn signal was on, there was hardly a visible turn signal on the trailer. There are two specific features of the Audi related to towing. First, the car should know when the trailer is connected. Second, the car shows warnings if trailer turn signals are burned out. The first feature worked, but the car would report burned out trailer turn signals any time I would signal while applying the brake. To fix the bulb burned outinch warning, I bought a pair of RK-506 to fix the warning. I realized before installing that since the warning only shows when the signal is on AND the brake is applied, I dont think this is a problem with the current draw of my trailers LED turn signals, but rather a bad attempt at combining the brake light and the turn signals. I did some more reading and bought RM-732. The Left, Right, Brake, and Ground wires from the European harness are wired to the input of the RM-732. The 1 Left+Brake and 2 Right+Brake output wires join one of the 3 tail light wires from the European harness, a 4 ground wire from a common ground on the vehicle, and a 5 12v fused wire from the battery and run to the US 7 blade connector beneath the vehicle. I dont need the 6 trailer brake or 7 backup lights for my trailer. All of the wiring seems to work fine, but I have more problems with the Audis onboard systems. It now believes that a trailer is connected all the time and I get bulb burned outinch warnings every time I use the turn signals brakes or no brakes - and no trailer connected either! What is the right way to convert a European 7 pin wiring harness to a US 7 blade wiring harness, such that: 1. Turn signals are still visible on the trailer when the brakes are applied 2. There are no bulb burned outinch warnings ever 3. The car only believes a trailer is connected when a trailer is actually connected

asked by: Christian