Hi, the problem is I don't know what old coaches used in 1993 for battery control. I suspect it would have used a basic high current continuous duty relay with a switch on the dash or near the door that controlled it (turns on to allow converter to charge the batteries). You might have to see if some of the folks with older coaches comment on the forum to assist you.
I am attaching a basic generic 12vdc battery schematic for a more modern coach......it shows your two 6 volt batteries wired in series as well as some more modern devices (latching relay and emergency start relay) used to control batteries. It shows just the main DC portions; no 120vAC is shown. It may help you visualize the potential connections, but your coach is likely different. Also I don't know what your electrical experience is around batteries, but be very careful as they can vaporize a metal finger ring or watch band in seconds with severe burns resulting if you are not careful when wiring/using them. Good luck.
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