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 , in particular an NTC thermistor, wherein said temperature sensor 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 (S1) 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 ; 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 (S4) measured by said at least one temperature sensor ; and - comparing the obtained temperature test value (S4) with a predetermined temperature threshold (Tt); and wherein the test routine is considered not being successful, when the obtained temperature test value (S4) 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 , in particular an NTC thermistor, wherein said temperature sensor 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 (S1) 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 ; 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 (S4) measured by said at least one temperature sensor ; and - comparing the obtained temperature test value (S4) with a predetermined temperature threshold (Tt); and wherein the test routine is considered not being successful, when the obtained temperature test value (S4) is above a predetermined threshold. - receiving a starting signal (S1) 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 ; 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 (S4) measured by said at least one temperature sensor ; and - comparing the obtained temperature test value (S4) with a predetermined temperature threshold (Tt); and <EOS>