Mechanical Thermostats operate on the principle that gas in a sealed tube expands and contracts with the temperature. One end of the tube is attached to the evaporator, and the pressure expands or contracts bellows within the thermostat, which act on a switch to open or close the thermostat. Mechanical thermostats are set either to refrigerator or freezer temperature ranges.
Digital Thermostats utilize a sensor mounted within the box where it measures the temperature of the air and sends it to a remote digital display. Digital thermostats are very accurate and steady temperatures can be achieved easily. Digital thermostats can also be set to either refrigerator or freezer temperatures, which is very handy when cruising.