Hoping for some help on this... I have a 2001 ml320 with what appears to be a factory installed towning package. It has the round 7wire harness and 2" reciver type hitch.

My problem is that I cannot locate any type of brake gain control. At this point whenever I hookup a trailer with electric brakes, just a slight tap on the vehichle brake will lock up the trailer brakes.

I have looked in every nook and cranny of the vehicle but can't locate it? Has anyone had a similar issue? Or do you know wher the control unit(sensitivity/gain) is "normally" located...

Thanks!

m

 

2 yrs later, I HOPE you're still a member here, or someone can help. You've described the EXACT issue I'm facing. 01 ML320 w/ factory hitch and harness. Haven't installed a controller yet (or is there one hidden already?). When I touch the brake pedal, trailer brakes lock up.

Is there a hidden brake controller w/ a slider somewhere? or at least is there a simple brake signal under the dash where we just cut into and connect the blue out from a Reese controller?

 

I have the info but had no luck oploading it here. Let me know your e-mail address and I will forward it to you. Original Mercedes service bulletin: "Recommended wiring procedure during brake controller installation."
Bernard