Take out that plastic drip tray so the cold air from underneath the freezer can drop down. The thermostat is there and the tray holds the cold and then the fridge cycles off to soon.
I wired mine directly to a battery source. No ignition switch in between. That slight break in the circuit when you go to crank will cause the Garmin to shut down. Connect ground under the dash and run the positive to the battery of choice. It happened to me on an previous Four Winns I had.