The principle of activity is the same at all heaters. In the case that the temperature of the coolant is low there is a switching on the heating coils and circulating pump. Heating coil is in operation until the temperature of the coolant reaches 60°C, at this moment, occurs to turn off the coils and re-circulating pump. As soon as the fall temperature below 55°C again leads to switching on of the coils and the circulating pump and the process is repeated. Heaters with continuous pump mode have the pump running regardless of whether the spiral is in operation or not. If the thermostat is damaged and the appliance constantly heats up the coolant, the device is equipped with a thermal fuse that reacts at a critical temperature of 100 ° C when the entire device is switched off.