The heater is first controlled by the air conditioning master switch. When the air conditioning switch is turned on, the current flows from the battery positive electrode through a master insurance, through the ignition switch IG, and then to the central circuit board, and then through an air conditioning insurance to the air conditioning switch. There are several routes out of the air conditioning switch. Warm air blower of the air conditioning out again to the circuit board inside turn on the heater relay coil Then take iron coil magnetic field make contact The heater in accordance with the current of heater's speed is then from central within the circuit board through an insurance through relay contact to the heater switch From the heater switch out four wires 1 2 3 4 transmission line, respectively To speed control resistance resistance of the top line heater so that the rotating gear current from different lines flow