I ran tests today on your suggestions:
I used a volt meter at the solenoid in the RV battery control center. zero voltage with ignition key off, then I started the engine and....no joy.
The solenoid in the RV battery control center clicked when I turned the key indicating that the circuit was closed and alternator current should be available, but the voltage to the house batteries stayed the same and the Victron still showed a net loss of amperage as before I started the engine.
So I started looking upstream in the Chevy 4500. Clearly the alternator is working because 14.4 volts were going to the chassis battery.
The chevy 4500 fuse diagrams mention two "Auxiliary'' circuits, each with its own fuse and a relay. I only had time to check one of them, a 50A fuse & relay. That relay clicked when I turned on the key and the fuse was good. No problem there, no Eureka moment either.
That leaves me with only one candidate, the other Aux circuit in the Chevy fusebox. I'll check that in the morning but if that isn't it I'm not sure where to look next.
I also tested the theory that the alternator wouldn't charge the house until the chassis battery was fully charged,
- I charged the chassis battery up to full power using a charger.
- I pulled the new house battery bank down to 12.4 VDC using the inverter to power a household 120v fan for a few hours.
Thanks everyone for your ideas on this.
-Grouchy
