A method for controlling a heating system component of a heating system for heating a fluid medium, said heating system component comprising: a carrier unit; a heating unit coupled to said carrier unit; and a controller; wherein said carrier unit comprises a wet side and a dry side, wherein said wet side corresponds to a surface of said carrier unit configured to be in contact with said fluid medium, wherein said dry side is located on a surface opposite to said wet side; and further comprising at least one temperature sensor (170a, 180a, 180b, 270, 370, 470), in particular an NTC thermistor, wherein said temperature sensor (170a, 180a, 180b, 270, 370, 470, 480) is effectively in thermal contact with at least a part of an upper surface of said dry side of the carrier unit, the method comprising: - receiving a starting signal at the controller for starting heating of the heating system component; characterized in that the method further comprises: - carrying out a test routine for at least the at least one temperature sensor (170a, 180a, 270a, 370a, 460, 470a, 480, 770); and - in case the test routine is not successful: entering a safe state of the heating system component; wherein the test routine includes: - powering (6, S3) the heating unit with a predetermined test power level (Pt) for a predetermined test time period (Th); - obtaining a temperature test value measured by said at least one temperature sensor (170a, 180a, 270a, 370a, 460, 470a, 480, 770); and - comparing the obtained temperature test value with a predetermined temperature threshold (Tt); and wherein the test routine is considered not being successful, when the obtained temperature test value is above a predetermined threshold. said heating system component comprising: a carrier unit; a heating unit coupled to said carrier unit; and a controller; wherein said carrier unit comprises a wet side and a dry side, wherein a carrier unit; a heating unit coupled to said carrier unit; and a controller; wherein said carrier unit comprises a wet side and a dry side, wherein said wet side corresponds to a surface of said carrier unit configured to be in contact with said fluid medium, wherein said dry side is located on a surface opposite to said wet side; and further comprising at least one temperature sensor (170a, 180a, 180b, 270, 370, 470), in particular an NTC thermistor, wherein said temperature sensor (170a, 180a, 180b, 270, 370, 470, 480) is effectively in thermal contact with at least a part of an upper surface of said dry side of the carrier unit, the method comprising: - receiving a starting signal at the controller for starting heating of the heating system component; characterized in that the method further comprises: - carrying out a test routine for at least the at least one temperature sensor (170a, 180a, 270a, 370a, 460, 470a, 480, 770); and - in case the test routine is not successful: entering a safe state of the heating system component; wherein the test routine includes: - powering (6, S3) the heating unit with a predetermined test power level (Pt) for a predetermined test time period (Th); - obtaining a temperature test value measured by said at least one temperature sensor (170a, 180a, 270a, 370a, 460, 470a, 480, 770); and - comparing the obtained temperature test value with a predetermined temperature threshold (Tt); and wherein the test routine is considered not being successful, when the obtained temperature test value is above a predetermined threshold. - receiving a starting signal at the controller for starting heating of the heating system component; - carrying out a test routine for at least the at least one temperature sensor (170a, 180a, 270a, 370a, 460, 470a, 480, 770); and - in case the test routine is not successful: entering a safe state of the heating system component; - powering (6, S3) the heating unit with a predetermined test power level (Pt) for a predetermined test time period (Th); - obtaining a temperature test value measured by said at least one temperature sensor (170a, 180a, 270a, 370a, 460, 470a, 480, 770); and - comparing the obtained temperature test value with a predetermined temperature threshold (Tt); and