Hi. Does your BCC look “something like” the attached RV Custom Products BCC picture?
With new batteries you say that the converter can charge both house and chassis batteries OK. Then I think the interconnect relay is also working OK (it ties both batteries together under control of BCC circuitry). Then you say that when the engine is running (and converter AC is off I assume), the alternator charges the chassis battery OK, but not the house battery. So that would seem to indicate that the interconnect relay is not operating in that particular situation. If you have the RV Custom BCC there is a time delay before the interconnect relay is operated of a few minutes after proper charging voltage is detected (either via the converter or via the alternator). Make sure you wait a few minutes for the sense and cutover. It might be possible that the voltage sensing diode from the chassis battery charge side has opened or some part of the sense circuit has failed on the chassis battery side. You could also try operating your emergency start switch to force the interconnect relay to operate when running the engine to see if the house batteries now see the alternator voltage.
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