The first 6 ot 7 times the REAR AC went out, it was replaced for free, under warranty. Now, we have to pay for it and I am seriously considering a rooftop mounted, 12v RV ac unit. Has anyone ever tried that? There are dozens of videos on YouTube that show what to buy and how easy it is to install. But there's not a lot of info out there on how to power the unit. Can we hook up a rooftop AC unit directly to the power that is running to the stock rear AC unit behind the driver's seat??