FUEL CELL SYSTEM

An FC system disclosed herein comprise FC units, a cooler and a controller. Each of the FC units comprises a FC stack, a supply/a return/a circulating passages through which refrigerant flows and first to third temperature sensors. The first to third temperature sensors measure temperatures of the refrigerant in the passages at different positions. The controller is configured to stop a specific FC unit, compare measured values of the first to third temperature sensors of the stopped specific FC unit and, when one of the measured values differs from the other two of the measured values, provide notification about malfunction of the temperature sensor with the different measured value.