Part 2 of 2

BLOWER MOTOR SWITCH
The A/C Heater blower motor is controlled by a rotary-type blower motor switch, mounted in the A/C Heater control panel On vehicles with manual temperature control systems, the switch allows the selection of four blower motor speeds, but will only operate with the ignition switch in the ON position and the A/C Heater mode control switch in any position, except OFF. On vehicles with the Automatic Zone Control (AZC) systems, the switch allows the selection of Lo Auto, Hi Auto, and ten speed settings between Lo and Hi.

On manual temperature control systems, the blower motor switch is connected in series with the blower motor ground path through the a/c heater mode control switch. The blower motor switch directs this ground path to the blower motor through the blower motor resistor wires, or directly to the blower motor, as required to achieve the selected blower motor speed.

On AZC systems, the blower motor switch is just one of many inputs to the AZC control module. In the manual blower modes, the AZC control module adjusts the blower motor speed through the blower motor controller as required to achieve the selected blower switch position. In the auto blower modes, the AZC control assembly is programmed to select and adjust the blower motor speed through the blower motor controller as required to achieve and maintain the selected comfort level.

The blower motor switch cannot be repaired and, if faulty or damaged, it must be replaced. The switch is serviced only as a part of the a/c heater control assembly.

IN-CAR TEMPERATURE SENSOR
Models equipped with the optional Automatic Zone Control (AZC) system use automatic dual zone temperature control with infrared sensing technology. The temperature sensor is located in the center instrument panel, between the dual temperature knobs of the AZC.

The Automatic Zone Control uses infrared sensing technology to control occupant comfort levels, not the actual passenger compartment air temperature. Dual infrared sensors mounted in the face of the control unit independently measure the surface temperature to maintain customer-perceived comfort temperature under changing conditions. Dual Zone temperature control provides wide side-to-side variation in comfort temperature to exceed the needs of either front seat occupant. This sensing system replaces interior air temperature and solar sensors used to approximate direct sensing control through complex control programs.

The infrared temperature sensor cannot be adjusted or repaired and, if faulty or damaged, the AZC head must be replaced.

NOTE: The infrared sensor window may be permanently damaged if any type of cosmetic vinyl dressings are allowed to contact the lens. Avoid spraying or wiping this area with any cleaner or conditioner. This may result in impaired temperature sensing and control.

BLEND DOOR ACTUATOR
The blend door for all models is actuated by an electric actuator, while the AZC system uses 2 separate actuators to allow the driver and passenger to select individual comfort levels. In the following procedures, service for both types of actuators is covered.

RECIRCULATION DOOR ACTUATOR
The recirculation door actuator for vehicles equipped with the standard equipment manual temperature control system is vacuum controlled. The optional Automatic Zone Control (AZC) system uses an electric recirculation door actuator. In the following procedures, service for both types of actuators is covered.

VACUUM CHECK VALVE
Two vacuum check valves (non AZC only) are installed on the vacuum supply system One is on the accessory vacuum supply line in the engine compartment, near the vacuum tap on the engine intake manifold. A second vacuum check valve is located on the bottom of the HVAC unit behind the passenger front floor duct on the black vacuum line. The vacuum check valves are designed to allow vacuum to flow in only one direction through the accessory vacuum supply circuits.

The use of a vacuum check valve helps to maintain the system vacuum needed to retain the selected A/C Heater mode settings. The check valve will prevent the engine from bleeding down system vacuum through the intake manifold during extended heavy engine load (low engine vacuum) operation.

The vacuum check valve cannot be repaired and, if faulty or damaged, it must be replaced.

Fig.22 Vacuum Reservoir:

VACUUM RESERVOIR
The vacuum reservoir is mounted in the right front of the vehicle behind the headlamp mounting module. The headlamp mounting module and headlamp assembly must be removed from the vehicle to access the vacuum reservoir for service. Refer to Lamps/Lighting for the procedures.

Engine vacuum is stored in the vacuum reservoir. The stored vacuum is used to operate the vacuum-controlled vehicle accessories during periods of low engine vacuum such as when the vehicle is climbing a steep grade, or under other high engine load operating conditions.

The vacuum reservoir cannot be repaired and, if faulty or damaged, it must be replaced.

EVAPORATOR TEMPERATURE SENSOR
The evaporator probe is a 2 wire temperature sensing element located at the coldest point on the face of the evaporator. The switch is attached to the evaporator coil fins. The evaporator temperature probe prevents condensate water on the evaporator coil from freezing and obstructing A/C system air flow.

The probe is used to switch the clutch OFF before evaporator freeze-up occurs. Output from the probe is sampled by the Body Control Module (BCM). The clutch is switched OFF when the probe temperature reaches 1.1 °C (34 °F). It is allowed to switch ON when the probe temperature reaches 2.2 °C (36 °F).

BLOWER MOTOR
The blower motor and blower wheel are located in the passenger side end of the HVAC housing, below the glove box module. The blower motor controls the velocity of the air flowing through the HVAC housing by spinning a squirrel cage-type blower wheel within the housing at the selected speed. The blower motor and blower wheel can be serviced from the passenger compartment side of the housing.

The blower motor will only operate when the ignition switch is in the ON position, and the a/c heater mode control switch is in any position, except OFF. The blower motor circuit is protected by a fuse in the junction block. On models with the standard manual temperature control system, the blower motor speed is controlled by regulating the battery feed through the blower motor switch and the blower motor resistor. On models with the optional Automatic Zone Control (AZC) system, the blower motor speed is controlled by using Pulse Width Modulation (PWM). The blower motor controller adjusts the battery feed voltage to the blower motor, based upon an input from the blower motor switch, through the AZC control module. Pulse width modulation of blower power allows the blower to operate at any speed from stationary to full speed.

The blower motor and blower motor wheel cannot be repaired, and if faulty or damaged, they must be replaced. The blower motor and blower wheel are each serviced separately.