There are many reasons why your Sub-Zero refrigerator may have stopped working. The most common reason Sub-Zero fridges stop working is a lack of maintenance. You need to clean the condenser coils in your refrigerator every 3-6 months. These coils are in charge of chilling the refrigerant, which generates cool air for the refrigerator. Dusty coils are less capable of cooling refrigerant, resulting in a Sub-Zero refrigerator that needs repairs.