The problem with your explanation is that the emergency start switch works without the coach being on shore power or generator or the engine running. If that is so, the voltage in the chassis battery is below 13.2v so it cannot open the Trombetta. You must be on shore power/generator or the engine must be running for the batteries to be above 13.2v necessary to open the Trombetta. The emergency start switch works at below 13.2v so it must tie the two battery systems together directly. I don't see any other way no matter what the Thor diagrams say.
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