Method for operating a gas burner

Method for operating a gas burner (10), wherein during burner-on phases a gas/air mixture having a defined mixing ratio of gas and air is provided to a burner chamber (11) of the gas burner (10) for combusting the gas/air mixture within the burner chamber (11), wherein the gas/air mixture is provided by mixing an air flow sucked in by a fan (14) with a gas flow, and wherein the defined mixing ratio of the gas/air mixture is controlled by comparing an actual value of a signal provided by an electrical or electronic sensor (23) coupled to a gas duct (16) with a nominal value for the signal provided by the electrical or electronic sensor (23) and by generating a control variable for a gas valve (17) assigned to the gas duct (16) on basis of the control deviation between the actual value and the nominal value. During burner-on phases the function of the electrical or electronic sensor (23) becomes checked by generating an input variable for an actuator (21) of the gas valve (17), by operating the gas valve (17) on basis of the input variable for the actuator (21) and by comparing an actual output signal provided by the electrical or electronic sensor (23) in response to this operation of the gas valve (17) with a nominal output signal expected in response to this operation of the gas valve (17).