I'm assuming you are following the directions listed in your owners manual...correct? Supplemental braking devices that plug into your toad's cigarette lighter do draw a lot of amperage from the battery and in these cases, you really need to have a 12v line from the motor home's battery(s) to the toad's battery. Most motor homes have this wire going to the 7-pin connector, but may not be connected. Check the voltage on, I believe, pin 4.
Good luck
Ron
ps... the "tow" vehicle is the vehicle "doing" the towing...not the one "being" towed. Hence the name "toad".
Ron & Sandie
2013 Tiffin Phaeton 42LH Cummins ISL 400hp
Toad: 2011 GMC Terrain SLT2
Tow Bar: Sterling AT
Toad Brakes: Unified by U.S. Gear
TPMS: Pressure Pro
Member of: GS, FMCA, Allegro
RETIRED!! How sweet it is....