My C class frame engine charges my batteries 14.4 V. Emergency start switch only works one way, to give power to the frame engine battery to start V10 engine, so if my coach batteries are dead, can't use the emergency start switch to start generator. That's how mines wired to work.
I carry compact jumper unit from Harbor Freight, just in case needed to put power into coach batteries should they not have enough Umph to start generator. Haven' needed to use it yet and hope don't have to.
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