Our 420 came with 3 AC units installed. One's located in the bedroom, one in the bunk bed area, and the 3rd in the garage. I can have all three AC units on, but only two will run simultaneously. It will function the same whether running on the generator or shore power. We have one thermostat on ours that shows 3 zones. I will note that it gets cold as ice in that bunk area! I don't understand why Keystone put the AC unit there and not in the living area. I've found if I close the vents on that unit, it makes a tremendous difference (increase) in the amount of air flow coming from the vents in the living/kitchen area. Sorry, I couldn't be of more help.
Dennis & Jackie
2015 Ram 3500 Laramie DRW, 6.7L CTD
2016 Fuzion 420 Chrome Toy Hauler