Electronic Climate Control

The semi-automatic temperature control system is available as on option.

With the use of microcomputer, the control assembly analyzes inputs from the following major sources;
^ temperature, function and blower selections (made by the vehicle occupants).
^ in-vehicle temperature.
^ ambient temperature.
^ temperature control lockout valve and switch.
^ A/C sunload sensor.




Using these inputs, the microcomputer determines the correct conditions for the following outputs:
^ A/C clutch engagement.
^ lower speed.
^ A/C air temperature control door position.

An electronic blend door actuator is used to operate the A/C air temperature control door.
^ Vacuum control motors are used to control each of the three remaining air distribution doors.
^ A feedback circuit is used in the electronic blend door actuator to supply the control assembly with A/C air temperature control door position information.
^ The blower motor is controlled by the control assembly through the Pulse Width Modulated (PWM) A/C blower motor speed control.
^ The A/C blower motor speed control reacts to the low power signal from the control assembly, which provides high power signal required to drive the blower motor. The system response chart shows the control assembly response to the function selections.

An electro-vacuum solenoid is used to direct source vacuum to the heater and A/C air inlet duct door. The heater and A/C air inlet duct door will close to outside air during cool/cold weather operation if the engine coolant is below approximately 45°C (113°F). This is to prevent outside air from entering the passenger compartment when the system is not capable of heating the incoming air. The solenoid is energized to close the heater and A/C air inlet duct door to outside air only if the following conditions exist:
^ control is on.
^ control is set at a non-A/C position (FLOOR or VENT).
^ blower knob is in the AUTO position.
^ the engine coolant temperature is below approximately 45°C (113°F).
^ control assembly selected temperature is between 18°C and 29°C (65°F and 85°F).

The solenoid will not be energized to close the heater and A/C air inlet duct door if any of the above conditions do not exist.

The heater and A/C air inlet duct door will also close to outside air in the OFF and MAX A/C positions by applying source vacuum through the A/C control.




A Self Diagnostics feature has been included in the control assembly to supply the technician with Diagnostic Trouble Codes (DTCs). These DTCs direct the technician to the inoperative component. Refer to Inspection and Verification. Initial Inspection and Diagnostic Overview

System Operation
The Semi Automatic Temperature Control (SATC) system automatically maintains the temperature selected for driving comfort. The system function and airflow discharge location must be manually selected by the vehicle occupants.
^ The system also provides the option of manually overriding the automatic operation of the A/C blower motor speed as desired.
^ Additionally, the system has an A/C sunload sensor for automatic solar sensitivity, resulting in temperature compensation during high sunload conditions.
^ The outside temperature can also be displayed at any time by momentarily pressing the OUTSIDE TEMP button. The outside temperature will then be displayed for four seconds.
^ For optimum automatic operation, the system should be in AUTO blower motor position and set to the desired temperature setting.
^ If passenger compartment temperature is warmer or cooler than the set temperature, the climate control system will automatically provide heat (when the engine is warm) or air conditioning, as required, to reach the comfort setting as fast as possible.
^ If it is necessary to adjust the comfort setting, the setting should be changed only in small increments (1-2 degrees) to maintain comfort and avoid large variations of in-vehicle temperature. Raising or lowering the set temperature in large increments from the comfort setting will not reduce the time required to reach stabilized comfort.

AUTO
In AUTO, the blower motor is controlled by the microprocessor. Blower speed is determined by the set temperature of the in-car temperature.

OFF
Rotating the function selector knob to OFF will turn the system off completely. The digital display window will be blank.

Digital Display Window
The digital display window will indicate one of three displays depending upon the manual selection:
^ selected temperature.
^ outside temperature.
^ blank when system is off.

NOTE: Diagnostic codes are only displayed when control is in self-test.

Diagnostic Trouble Codes are displayed after control unit has executed self test.

WARM (Red) Button
The WARM (red) button is used to raise the temperature setting.
^ Pressing the button once will raise the temperature one degree.
^ Holding the button in will continuously raise the temperature setting in one-degree increments to 29°C (85°F) and then will jump to 32°C (90°F) in one step for continuous maximum heating.

COOL (Blue) Button
The COOL (blue) button is used to lower the temperature setting.
^ Pressing the button once will lower the temperature one degree.
^ Holding the button in will continuously reduce the temperature setting in one-degree decrements to 18°C (65°F) and then will jump to 15°C (60°F) in one step for continuous maximum cooling.

OUTSIDE TEMP
Depressing the outside temperature button will display the outside temperature for four seconds. After four seconds the display returns to the set point.

MAX A/C
The system directs cool, recirculated air through the A/C register on the instrument panel.
^ As the vehicle interior cools down, the discharge air temperature and fan speed will automatically and gradually change to maintain the set temperature (if automatic blower has been selected).

A/C
The system directs outside air through the A/C register on the instrument panel.
^ As the vehicle interior cools down, the discharge air temperature and fan speed will automatically and gradually change to maintain the set temperature (if automatic blower has been selected).

PANEL
On cool, sunny days, PANEL may be used to cool the vehicle interior. In PANEL position:
^ the blower motor will remain off until the engine is warm enough to provide heat.
^ the A/C compressor will not operate. PANEL/FLOOR.

In PANEL and FLOOR position, outside air is directed to the A/C register and heater outlet floor duct.
^ The control will automatically and gradually change the discharge air temperature and fan speed to maintain the set point (if automatic blower has been selected).
^ The A/C compressor will operate in ambient temperature above approximately 10°C (50°F).

FLOOR
In FLOOR position, the blower motor will remain off until the engine coolant reaches 45°C (113°F).
^ If in AUTO mode, the system will then direct outside air through the heater outlet floor ducts.
^ As the vehicle interior warms up, the discharge air temperature and fan speed will automatically and gradually change to maintain the set temperature (if automatic blower has been selected).

FLOOR/DEF
The system directs outside air through the:
^ windshield defroster hose nozzles.
^ heater outlet floor ducts.
^ A/C side window demister and hoses. Adjust A/C blower motor and set temperature as required to clear the windshield glass. The A/C compressor will operate in ambient temperature above approximately 10°C (50°F).

DEFROST
The system directs outside air through the windshield defroster hose nozzle and the A/C side window demister and hoses. The A/C compressor will operate in ambient temperature above approximately 10°C (50°F).