You say chassis battery charges fine when on shore power so the Trombetta (inter connect or isolator relay) is likely working for that charge mode, but when shore is off and you are running the engine/alternator does the Trombetta operate? Check charging voltages on both chassis and coach batteries with a voltmeter when running off alternator. Also check ground and sensing connections on Bird for clean and good connections. Attaching a good reference document with trouble shoot info.......might be the Bird that has crapped on you.
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