I think it would be the same as any auto assuming it's a 12-volt system. If it is a 12-volt system the battery's if charged should be at 13.2 volts You will need a multimeter set to DC volts, with the coach running check the voltage at the coach battery's They should read somewhere between 13.5 to 14.2 volts if itis charging. Turn on the headlights and blower motor, the voltage should stay in the 13.5 to 14.2 volts range. If the voltage falls off, I would pull the alternator of and have it checked at an auto parts store