A resistance heater 10 for a liquid system, in particular a fuel system of a diesel engine, in which a heating element 13 is connected to at least two contact rods 12a, 12b. Terminals are provided on the contact rods 12a, 12b so that they can receive an electric voltage. In addition, a sensor 24 is provided with which at least one parameter in the liquid system can be detected, and the sensor 24 is connected accordingly to at least one analyzer unit 18.