Dual vs Single AC units.

enblethen wrote:
Common?
You need to check to see what ducted outlets come off which AC unit. Yes, the bedroom one should only feed the bedroom, however it is possible that the duct from the bedroom unit may feed into hall or bath area.
Some thermostats or system allows the AC unit to switch automatically from AC units. This would allow the whole rig to stay cool, yet save energy by running only one at a time.

I can't speak for all ducted units, but all the ones that I've looked closely at (including mine) are all connected together. I can turn on my bedroom A/C and close the bedroom vents and it will push air to the front of the motorhome. I have done that before on hot days to get both units cooling the front. Also on hot nights I have turned off the rear unit and closed most of the front vents and let the front unit cool the bedroom. Makes for a quieter night without the A/C unit over your head running.