An automatic ice making machine includes a refrigeration system comprising a compressor, a condenser, an evaporator and an expansion device; a water system comprising an ice forming surface in thermal contact with the evaporator; and a control system comprising i) an on/off selector that causes the control system to either operate the compressor and water system so that the ice making machine automatically makes ice, or shuts the machine off until manually turned on; and ii) an automatic restart selector that causes the control system to shut down ice making for a predetermined period of time and then automatically resume ice making. Preferred embodiments of the a water system comprise a water filter and the control system comprises a filter change indicator, whereby an indication is displayed after a predetermined condition is reached indicating that the water filter should be replaced. Also, the control system preferably comprises a sensor to determine the temperature of the liquid line and a program that controls operation of the condenser fan during a harvest mode based on the temperature of the liquid line. Further, the preferred control board is changeable so that it can be used to appropriately control different models of ice making machines, with a microprocessor determining different durations of freeze and harvest cycles based on the same sensor temperature, depending on the changed aspect of the control board.