Method and assembly for operating an electrical heater of a catalytic converter system

A method of operating an electrical heater in a catalytic converter system, wherein the system is connected in an exhaust gas cleaning system downstream, as seen in an exhaust gas flow direction, of an internal combustion engine with an electronic engine control, wherein the electrical heater is supplied with an electrical current through a power switch operated by an electronic control, and wherein the electrical heater heats the system to or maintains the system above a minimum temperature necessary for catalytic conversion, the method which comprises:

• a) measuring a temperature of a catalytic converter and utilizing the temperature as a controlled variable of at least two different control circuits comprising a first control circuit and second control circuit;
• b) defining at least one first control circuit from the at least two different control circuits, and controlling a catalytic converter system in regular operation with the first control circuit;
• c) automatically monitoring an operation of the first control circuit for malfunction;
• and
• d) if a malfunction is detected, automatically transferring control to the second control circuit of the at least two control circuits.