[Dennis4809]

Your engine alternator should charge all the batteries, coach and chassis. Yes, the coach batteries are the starter batteries for the generator but if they were to get to low to start the gen then you can start the engine long enough to get the gen to fire off.
If you have a volt meter, you could take a reading on both posts of the relay. If identical then it would seem that it's energized. Could then pull the control wire to see if it changes states.