I would suggest you check the grounding of the system to the frame. This is as important as the 12+ feeder. Check all connections for corrosion all the way from the battery to the joystick to pump motor.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7