Bill,
That makes sense. I assume you meant to say to pull the 15 amp "fuse", which should disable the thermostat. I didn't get any manual with the trailer, but contacted Dometic and received their operating instructions. The 35DSRL is equiped with a remote analog thermostat, but there is no mention of any 12 volt operating requirements.
Now if I can only figure out how to close off some of the ceiling ducts.........thanks