The invention relates to a heating system component (100) for a heating system for heating a fluid medium, with a carrier unit (110), and a heating unit (120) coupled to said carrier unit (110), and a controller; wherein said carrier unit (110) comprises a wet side and a dry side, wherein said wet side corresponds to a surface of said carrier unit (110) configured to be in contact with said fluid medium, wherein said dry side is located on a surface opposite to said wet side. A temperature sensor (170a, 180a, 270a, 370a, 460, 470a, 480, 770), in particular an NTC thermistor, is effectively in thermal contact with at least a part of an upper surface of said dry side of the carrier unit (110), the method (1) comprising: receiving (2) a starting signal (S1) at the controller (30) for starting the heating system component (100); carrying out a test routine (3) 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 (16) of the heating system component.