I have a question about using my reverse-cycle AC/heat to heat the cabin while away. I have a Cruisair SMXir keypad and expected that when I set the temperature to 55 degrees (lowest available temperature setting), set the control to heat, and the fan to auto, that the unit would not come on unless the temperature in the cabin dipped below 55 degrees. However, in a test yesterday afternoon, with the cabin temperature at 74 degrees, the unit still operates with what feel like cool air coming out. I ran it for oven an hour and it never stopped running. What am I doing wrong or what's not functioning properly?