Heating and Air Conditioning: Description and Operation

In the RUN position, the ignition switch connects circuit A1 from fuse 4 in the Power Distribution Center (PDC) to circuit A22. Circuit A22 powers a bus bar in the fuse block that supplies voltage to circuit C1 through fuse 12.

A heater-off switch in circuit C1 opens when the heater controls are in the VENT position. When the heater-off switch closes, circuit C1 supplies battery voltage to the blower motor switch. The switch sets blower motor speed to HIGH, MEDIUM, LOW or OFF.

The switch connects to the blower motor resistor block in the LOW and MEDIUM positions and directly to the blower motor in the HIGH position. The resistor block contains two resistors connected in series. Circuit C7 connects the resistor block to the blower motor.

From the blower motor resistor block, circuit C7 is double crimped at the HIGH terminal of the blower motor switch. Circuit C7 continues to the blower motor from the blower motor switch.

When the blower motor switch is in the LOW position, it supplies voltage to the resistor block on circuit C4. From circuit C4, voltage passes through both resistors in the resistor block to the blower motor on circuit C7.

In the MEDIUM position, the blower motor supplies voltage to the resistor block on circuit C5. From circuit C5 voltage flows through one resistor to the blower motor on circuit C7.

In the HIGH position, the blower motor switch connects directly to the blower motor on circuit C7. Voltage does not pass through the resistor block.

Circuit Z1 provides ground for the blower motor.