The blower motor controls operate by supplying ground to the motor through the blower speed switch contacts through the blower resistor. Battery voltage is available to the blower relay coil from Circuit Breaker #6 when the ignition switch is in the RUN position through the BRN (198) wire. Relay contact power is provided by Circuit Breaker #24 for the operation of the blower motor any time the ignition is in the RUN position. Motor speed is controlled by routing the blower motor ground through dropping resistors. The blower motor speed switch supplies ground through one of the resistors for all speeds but HIGH.

With the blower motor switch in the LO position, voltage is applied from the switch contacts through the BLU/WHT (180,196) wire to the blower motor resistor. The blower motor current flows through all three resistors in this switch position. The grounding is provided through the switch common terminal through the HVAC controller module. Current flow is established at which point the blower motor operates. Voltage drop through the three resistors in the blower motor resistor limits motor operation to its lowest speed.

With the blower motor switch in the MED LO position, voltage is applied to the blower motor resistor through the BLU/BLK (181,195) wire. Current flows through only two resistors to get to the motor. The motor operates at a faster speed than through all three resistors.

With the blower motor switch in the MED HI position, voltage is applied to the blower motor resistor through the BLU/YEL (182/194) wire. Current flows through only one resister to get to the motor. With the increased voltage at the motor, the motor operates at a still faster speed.

With the blower motor switch in the HI position, voltage is applied directly to the blower motor through the BLU/RED (183/192) wire. Current flows directly to the motor. With the maximum voltage at the motor, the motor operates at the fastest speed.

The HVAC temperature actuator controls the amount of engine coolant available to the heater core. The operator heat selection lever position is translated into an electric signal. The temperature actuator controls a motor operated valve in the engine coolant line. The valve is driven open in order to provide more heat energy (or closed for less heat) in response to the operator temperature selection.