Bounders of that era, only one a/c will run at a time by design. There should be a switch that say's 'front', 'rear', you turn the switch to the desired a/c unit you want to use. its possible that switch you should have, may be failing, allowing current to both units. My Bounder works opposite of yours, I can get both units to run when on the generator, but only 1 when on shore power, I dont use both when on gen. because it is a full load, and after a few minutes, the gen. slowing losses the battle and lugs down.
Where We Go 1 We Go All
1995 Bounder 35 UWB, F53