Are you sure no wiring has been crossed up from house and chassis battery connections? There are solenoids that are closed for charging controlled through Bi-directional Isolator Relay Delay (BIRD) and sometimes also as a boost switch.
This Battery Charge Controllers
may be of some help but be sure there are no added circuits connected to the chassis that should be connected to the house battery bank. Also be sure that the battery banks are in good condition. Check your CO Detector and see if there are two 12vdc positive leads on it. One is connected to chassis and on is connected to house and many times is routed around battery disconnects. Let us know what you find.
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