Trailer Brake Wiring Sprinter chassis

[Horizon170]

Class "C" towing a Dolly. 7 pin connector on RV and 7 pin connector on Dolly.
For those of you that have Freightliner/Sprinter Chassis-------Do you have a brake controller going to the 7 pin connector?
I chased the BLUE wire from the 7 pin to under the drivers seat.
I removed the drivers seat and discovered a huge Birds Nest of wiring and fuses.
The 4 normal trailer wires were connected to a Europe/USA converter, which is fine. White,brown, yellow, green----no special order.

Under the seat is the Blue wire connected to a blue w/white or yellow stripe that goes somewhere up front. I haven't traced it yet. I think I need to disconnect this Blue w/white stripe wire as I have no idea what it is for. Maybe one of you knows.
Here is a link to what I should do to connect it.Brake diagram
Does anyone have a better idea?
Thanks, Marvin
EDIT-------What is a good controller, not too expensive.

[Horizon170]

I found the green plug (4 wires) and Coachmen didn't use it.
They only connected a tail light converter (4 other wires)to the 7 pin rear trailer connector.
I will check the green for Ground and B+ although I fear that I will have to do all the wiring myself as the BLUE brake wire is not part of the green plug.
Any Ideas on which controller to buy?
Marvin

[road-runner]

Whatever trailer wiring you have will have been installed by Coachmen, so only somebody with a Coachmen Sprinter motorhome will be able to give specific advice. There are 2 possibilities: (1) They used the optional Sprinter trailer harness, or (2) They did their own custom wiring. On mine, Fleetwood did their own custom wiring, relaying all of the connections to the trailer connector (required on Sprinter), and adding a relay logic circuit to convert the 2-lamp stop+turn setup on the Sprinter to a single light setup. They did provide a blue wire to the brake pin on the trailer connector, buried and hidden with no instructions whatsoever.

[midnightsadie]

had a problem with my lights ,the power for that mess under the seat comes from two wires that run to the battery. don,t no about the blue wire. might google it or go to the sprinter source site ,they,d know.