Part 2 of 4

MODE DOOR ACTUATOR
The mode door actuator is an electric motor. It mechanically positions the panel/bi-level door and the heat/defrost door. The actuator is mounted to the bottom of the HVAC housing on the left side.

A potentiometer in the actuator allows the BCM (for both manual and ATC systems) to know the exact position of the doors at all times. The actuator is not serviceable and must be replaced if found to be defective.

RECIRCULATION DOOR ACTUATOR
The recirculation door actuator is an electric motor. It mechanically positions the recirculation door. The actuator is mounted to the right side of the HVAC housing.

A potentiometer in the actuator allows the BCM (for both manual and ATC systems) to know the exact position of the door at all times. The actuator is not serviceable and must be replaced if found to be defective.

BLOWER MOTOR RESISTOR BLOCK
The blower motor resistor is mounted to the lower right side of the heater-A/C housing in the passenger compartment, where it can be accessed for service.

The blower motor resistor has multiple resistor wires, each of which will change the resistance in the blower motor ground path to change the blower motor speed. The blower motor switch directs the ground path through the correct resistor wire to obtain the selected blower motor speed. The blower motor resistor cannot be repaired and, if faulty or damaged, it must be replaced.

With the blower motor switch in the lowest speed position the ground path for the motor is applied through all of the resistor wires. Each higher speed selected with the blower motor switch applies the blower motor ground path through fewer of the resistor wires, increasing the blower motor speed. When the switch is in the highest speed position, blower motor resistor is bypassed and the blower motor receives a direct path to ground.

BLOWER MOTOR POWER MODULE
The blower motor power module is mounted to the right side of the heater-A/C housing in the passenger compartment. The module provides the ground path to change the blower motor speeds. The blower motor power module cannot be repaired and must be replaced if faulty.

With the blower motor switch in the lowest speed position the ground path for the motor is applied through the module. Each higher speed selected the module applies a increase in ground which, increases the blower motor speed.

THERMAL LIMITER SWITCH
The thermal limiter switch measures compressor surface temperature. If compressor surface temperature is excessive, the switch cuts battery feed to the compressor clutch coil. The switch reset itself, once compressor surface temperature returns to normal. The switch is not adjustable or serviceable, if faulty the compressor must be replaced.

The thermal limiter switch interrupts battery feed to the compressor clutch coil when temperature reaches 122 - 128 °C (250 ° - 260 °F). The switch restores clutch coil battery feed when the temperature drops to 104 - 116 °C (220 ° - 240 °F).

HVAC HOUSING
The HVAC housing is mounted under the instrument panel to the dash panel. It houses the heater core, evaporator coil, blower motor and a series of doors. The doors are used to direct air from the blower motor to verious duct and through the heater core/evaporator coil.

The system draws outside air through the cowl opening at the base of the windshield. It then flows into the plenum chamber above the Heater A/C unit housing and passes through the evaporator. At this point airflow can be directed either through or around the heater core. This is done by adjusting the blend-air door with the TEMP control on the control head. After the air passes the blend air door, the air flow is then directed from the PANEL, BI-LEVEL (panel and floor), and FLOOR-DEFROST outlets. Air flow velocity can be adjusted with the blower speed selector switch on the control head.

Ambient air intake can be shut off by closing the recirculating air door. This will recirculate the air that is already inside the vehicle. This is done by rotating the RECIRC. knob on the control head. Rotating the MODE control knob to the Defrost/Floor or Defrost setting on the control head will engage the compressor. This will send refrigerant through the evaporator, and remove heat and humidity from the air before it goes through the heater core. The compressor can also be engaged by depressing the A/C button on the control head.