Look in the second attachment of my post #5 above which is the second part of the Tour Master Brochure. You will find in the page just prior to the floor plans under the "POWER" category that these coaches came standard with 2 each
engine batteries (what we call chassis batteries) and also 2 each
12 volt house batteries...as well as 4 each
6 volt golf cart sized batteries for the inverter. You need to restore that configuration of engine/chassis batteries to be assured of reliable starting under all temperature conditions.
You can always disconnect the cables from only one of the stacks and see what no longer gets power -- as the last hired worker may have had the concept of house and chassis reversed. The house batteries would normally be deep cycle, and the engine batteries would be high CCA starter types. Those batteries are a bit difficult to access, and that is why I added the watering fittings and squeeze bulb system to top them off during regular maintenance as it is nearly impossible to look down the cell cap opening to see the level. Here is a link to what I am talking about
I used a similar system for the 4 each golf cart batteries up under the windshield as they too were difficult to access.
I no longer own my coach, but maybe another Tour Master owner on this forum will chime in here with some useful pictures of the cable routing, etc.