PeachParts Mercedes-Benz Forum - View Single Post

jay_bob · #4 04-29-2019, 12:49 PM

I would highly recommend doing the factory hitch kit. There are software adjustments to the Powertrain operation that are engaged when you plug in the trailer lights. This would not occur with a 3rd party hitch.

Also the way they do rear lights on the newer Mercedes you will have a heck of a time just tapping in. They use LEDs with pulse width modulation, which is totally incompatible with regular bulbs. The way they do the trailer lights on the newer model is to provide a separate controller that is just fed with 12 V and the CAN bus signals, and it derives its own lighting signals independently of the vehicle lights.

I looked into doing this for our 2014 ML350, it is about $1500 in parts and you have to take half the interior apart to run the harnesses. But mechanically it bolts right in. You will also need Xentry to version code the rear SAM to accept the hitching mechanism controller. I think this can be done with a bootleg Xentry.

Also with a trailer that heavy you will need a brake controller.

We have a 2008 ML320 that has a factory hitch. It has the 7 pin connector and there is a plug up under the dash that you can buy a dealer harness for that accepts a 3rd party electric brake controller for the trailer brakes. I have only pulled lightweight trailers with this vehicle so I never retrofitted it for electric brake.

I did have to get a special 7 pin to 4 pin adapter that has compensation resistors for LED trailer lights for the ML320. The trailer outputs were expecting incandescent bulbs and they were absolutely driven crazy by LEDs. Got a ton of error messages on the dash about faulty trailer lights until I used the magic plug. I got this from e trailer dot com.