Patent ID: 8314364

Claim:
Method for operating an electric add-heater in a motor vehicle having at least one rechargeable electrochemical cell as a power source and an electric generator which is connected with the cell and is driven by a drive engine of the motor vehicle and by which an electric add-heater can be supplied with current when the drive engine is running, the method comprising in case of need, supplying the add-heater with current even when no current is supplied by the generator by switching over the add-heater to at least one electrochemical cell as a power source, that the charging condition of at least one electrochemical cell is monitored, and that the power supply of the electric add-heater realized by the at least one monitored electrochemical cell is interrupted again when the charging condition of the at least one monitored electrochemical cell has dropped below a preselected limit value, the add-heater being switched into closed air circuit by operation of a flap actuator when the add-heater is switched to at least one electrochemical cell as a power source.