The Big Boy charges both battery banks with the generator, plugged in, or driving down the road with the alternator when operating properly. It also combines both banks for starting purposes when using the boost mode. If the contacts inside have never been cleaned, or the whole unit has never been replaced, it is probably due. I clean mine about every two years. You can check proper function by measuring voltage on the two big lugs on the Big Boy. The reading should be within one tenth of a volt from one big lug to the other big lug. This will keep the batteries charged if operating properly, but it does not address your no start problem. The ignition switch might be failing is one possibility, there is also a relay on the starting Circuit Board in the rear run bay, next to the rear remote start switch. I believe that relay is soldered to the Circuit Board, so might need a competent person to repair that. If all the above check out, that relay is probably your problem. Also, as Eric stated above, in Coach Assist you will find how to service the Big Boy. I have two, when I remove one that needs cleaning, I rotate the second one in, and clean the other one so it is always ready to go when needed. Hope this helps, good luck!
