Dometic Ac keeps blowing 12 volt fuse

Depending on how your OEM wired the system. The AC system is protected by a 3 amp fuse ON the upper AC control board. That means YOUR fuse is shorted by the 12 volt wire run from the Roof top to the wall tstat. That said, you need to state WHICH Dometic control system you have. There are up to 6 or 7 different ones. Also, your Furnace may be on that 15 amp fuse and there is a short between the Furnace and the upper AC control board. You need to state if you have Phone type wire connections or standard 7 wire multi strand AC/Furnace wiring. Year/Brand/Model of RV will also help. Doug

PS. you just joined. ALWAYS list Year/Brand/Model of RV and Brand and MODEL of the appliance when asking for help.