How To Get A Separate Wire System On A 2011 Mercedes- Benz GL450 To Work On A Trailer 2 Wire System

Question:

I recently bought a 7 pin to 4 pin adapter for my 2011 GL450. My trailer lights work perfectly during the day when my headlights are off, but at night when my headlights turn on the trailer lights start flashing as if the hazards are on. The trailer lights are LED and I heard there can be some issues with these. Any thoughts on what’s going on? The first picture I sent is the adapter when the headlights are off. The left turn and right turn signal indicators are on. However when the headlights turn on the left, right, and tail light indicators start flashing.

asked by: Quinn S

Expert Reply:

It sounds like your trailer lights are a combined system and your vehicle lights are separate. Check your 2011 Mecedes-Benz G Class and see if the brake and turn signals are separate. The 2010 has separate taillight functions. This means that the brake, turn, and running light signals run on separate wires. If the trailer is combined that means that the right side wire, which is normally green, would have both the brake and turn signal running on one wire. Same would be for the left side and the running light circuit, which would be brown, would be on it's own wire.

If this is the case you would need to install the Roadmaster Brite-Lite Wiring Converter Item # RM-732. This will allow you to connect to the separate wires on the car and convert it to a 2 wire for the trailer.

When installing this it will require 4 Roadmaster Hy-Power Diode Item # RM-790. These need to be installed on the vehicle side.

I have included a link to a installation video, but it is on an RV so you want to make sure you test your wires to determine what wires you will need to connect to on your Mercedes. I have also included a link to a video to help show you where your taillight wires are and how to test them.

expert reply by: Shane H