Motorhomes (Diesel) do NOT have a quick connect like regular trucks for the Brake control. You should have a Roadmaster Chassis. We always run our own 12 gauge dual wire from the front to the rear, even if the chassis has the prewire to the rear. Some Diesels have a 2 wire pre wire to the rear. You still have to FIND those 2 wires in the harness at the dash area and it is extremely Difficult to do. So we run a harness from front to rear as it is quicker to do that, than it is to attempt to dig out the dash harness. We use the 2 wire to
1. Run the output brake signal to the rear
2. The 2nd wire is the Brake light signal which we splice at the rear brake light to send the signal to the brake control.
3. AT the dash you just connect the ground and the 12 volt positive to the brake controller with the 2 wires you ran.
The reason we like to use a 12 gauge separate harness is---running the BRAKE signal control 40 feet, use lose hardly any 12 volt signal strength with that 12 gauge wire. The factory harness if you can find it is usually 14 gauge and sometimes 16 gauge. Doug