Fuel cell system

A fuel cell system having a fuel cell, the system comprising:

• a first temperature sensor that measures a temperature of cooling water on a cooling water outlet side of the fuel cell;
• a second temperature sensor that measures a temperature of the cooling water on a cooling water inlet side of a water heater that heats the cooling water;
• a third temperature sensor that measures a temperature of the cooling water on a cooling water outlet side of the water heater;
• a cooling water pump that circulates the cooling water;
• and
• a control device that controls driving of the cooling water pump and the water heater by receiving measurement values from the first, second and third temperature sensors,
• wherein the water heater and the second and third temperature sensors are arranged above in a direction of gravity relative to the cooling water pump and the first temperature sensor, and
• wherein the control device is configured to determine that there is a cooling water leakage when a measurement temperature T1 measured by the first temperature sensor is not equal to a measurement temperature T2 measured by the second temperature sensor, or when the measurement temperature T2 and a measurement temperature T3 measured by the third temperature sensor have no temperature difference ΔT therebetween.