BCC: Battery Control Center. With the generator off and unplugged from shore power. Take your voltage readings there too. Start with the batteries. Then the voltage coming into your inverter. Next the voltage the three sides of your transfer switch.
Start with that. BCC should read the same 12.7 in and out, batteries 12.7, inverter 12.7. If voltage is less than 12.7 or zip your problem is between those two devices. Reset all fuses/breakers they might be half tripped. Reset inside your coach the main power fuse/breaker too.
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