System Description

DESCRIPTION AND OPERATION






Inputs
With the use of a microcomputer, the remote climate control module analyzes inputs from the following major sources:
^ The temperature, function, and blower selections (made by the vehicle occupants).
^ The in-vehicle temperature.
^ The ambient temperature.
^ An A/C sunload sensor.

Outputs
Using the inputs, the remote climate control module microcomputer determines the correct conditions for the following six outputs:
1. The A/C clutch engagement.
2. The blower speed.
3. The A/C air temperature control door position.
4. The heater air damper door position.
5. The windshield defroster door position.
6. The heater and A/C air inlet duct door position






Actuators
^ An A/C electronic door actuator motor 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 A/C electronic door actuator motor to supply the control assembly with the A/C air temperature control door position information.
^ The blower motor is controlled by the control assembly through the A/C blower motor speed control.
^ The A/C blower motor speed control is necessary to react to the low power signal from the control assembly to provide a high power signal required to drive the blower motor. The System Response Chart shows the control assembly response to the function selections.

An on-board 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.






Control Assembly
The following systems are integrated into a single control panel:
^ The AM/FM stereo radio.
^ The clock.
^ The rear window defroster switch.
^ The Electronic Automatic Temperature Control (EATC).
^ The full-logic cassette tape player.
^ The compact disc player control (optional).

The remote climate control module is mounted to the A/C evaporator housing behind the integrated control panel.

The integrated control panel is connected to the remote climate control module with a dedicated two-wire communication link.

The integrated control panel EATC features:
^ A Vacuum Fluorescent Display (VFD) for displaying set temperature, ambient temperature, function, and Diagnostic Trouble Codes (DTCs).
^ An electro-luminescent backlighting for all buttons and graphics.
^ Function override buttons.
^ Temperature control and blower speed rocker switches.

When the system is operating under AUTOMATIC control, the VFD display will show the preferred or target temperature to which the elements of the automatic control system respond.
^ A/C blower motor speed, under automatic control, varies in response to ambient temperature changes and a predetermined delay factor.
^ Temperature selection may be increased or decreased in one degree increments between 18° C (65° F) and 29° C (85° F) by pressing the TEMP rocker switch. The system will respond accordingly.

Other control assembly features include:
^ A 16° C (60° F) setting for maximum cool and a 32° C (90° F) setting for maximum heat.
^ An OUTSIDE TEMP button which, when pressed, will display the air temperature outside the vehicle.
^ An OFF button which, if pressed, will apply vacuum to close the heater and A/C air inlet duct door, shut off the A/C blower motor operation, and discontinue the climate control functions through the system.

When the (- FAN +) rocker switch is pressed, the blower motor speed will remain under manual control until the AUTO or MAX A/C button is pressed.
^ Under automatic control, the A/C blower motor speed varies as required to accommodate the total automatic functions in the system.
^ Under manual control, the A/C blower motor speed is constant-based on the rocker switch setting.

An illumination bulb in the control assembly provides backlighting for the Vacuum Fluorescent Display (VFD) window. When the panel dim control on the headlamp/parking lamp switch is adjusted, the intensity of the light from this bulb will increase or decrease depending upon the adjustment. (The backlighting on the control assembly, as well as in other instrument panel locations, will dim whenever the headlamp switch is in the HEAD position.

SYSTEM OPERATION
The electronic automatic temperature control system automatically maintains the temperature selected for driving comfort and regulates the airflow between the:
^ A/C registers.
^ Heater outlet floor ducts.
^ Windshield defroster hose nozzle.
^ A/C side window demister and hoses.






^ The system also provides the option of manually overriding the blower speed and/or airflow direction 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 until the OUTSIDE TEMP or any other button is pressed.
^ For optimum automatic operation, the system should be in AUTO mode and set to the desired temperature setting.
^ If the 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 to avoid large variations of the passenger compartment 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
The AUTO button functions in the following manner:
^ Pressing the button turns the system on for fully automatic operation.
^ The display window will be backlighted to show the selected temperature and AUTO.
^ The system maintains the selected temperature by:
- Controlling the airflow direction (functional setting).
- Controlling the airflow quantity (blower speed).
- Controlling the discharge temperature required for comfort with the A/C air temperature control door
^ When heating is required, airflow will automatically be directed through the heater outlet floor ducts and A/C side window demister and hose with a small amount of air through the windshield defroster hose nozzles.
^ During cool weather, the A/C blower motor operation will be delayed until the engine has heated sufficiently (about 49° C (120° F) engine coolant temperature) or for 3 1/2 minutes, whichever occurs first, to provide warm discharge temperatures.
^ The airflow will be directed through the instrument panel A/C registers when cooling is required.
^ The A/C registers can be adjusted for comfort. When maximum cooling is required, the system will automatically operate using recirculated air for rapid cool-down and automatically change to outside air as the vehicle interior temperature approaches the selected temperature.
^ In moderate conditions, the system will automatically operate with airflow directed through the heater outlet floor ducts and through the windshield defroster hose nozzles at a moderate A/C blower motor speed.

OFF
Pressing the OFF button:
^ Will turn the system off completely.
^ Leaves the digital display window blank unless OUTSIDE TEMP is selected.

DIGITAL DISPLAY WINDOW
The digital display window will indicate one of two displays depending upon the manual selection.
^ The selected function and comfort temperature.
^ The outside temperature.

TEMP
The TEMP button, used to raise or lower the temperature setting, operates as follows:
^ Rock the button once to the right to raise the temperature one degree.
^ Hold the button in continuously to the right to raise the temperature setting in one-degree increments to 29° C (85° F) and then jump to 32° C (90° F) in one step for continuous maximum heating.
^ Rook the button once to the left to lower the temperature one degree.
^ Hold the button in continuously to the left to reduce the temperature setting in one-degree increments to 18° C (65° F) and then jump to 15° C (60° F) in one step for continuous maximum cooling.

OUTSIDE TEMP
Pressing the OUTSIDE TEMP button will:
^ Display the outside temperature until the OUTSIDE TEMP or any other button is pressed.
^ If the set temperature is changed while the outside temperature is selected, the set temperature will replace the outside temperature on the display for four seconds, then revert to outside temperature.
^ If the system is turned OFF with the outside temperature selected or if the OUTSIDE TEMP button is depressed after the system is off, the outside temperature will be displayed in the digital display window. Pressing the OUTSIDE TEMP button will turn the outside temperature feature OFF and the digital display window will become blank (dark).






Manual Overrides
There are six manual override buttons along the lower edge of the integrated control panel. Each affects the system operation as follows:

MAX A/C
Pressing the MAX A/C button will show MAX A/C and the set temperature in the display window.
^ The heater and the A/C air inlet duct door will close to outside air allowing air from inside the vehicle to be drawn into the system.
^ The A/C clutch will operate if the ambient temperature is approximately 10° C (50° F) or above.

VENT
Pressing the VENT icon button will show the VENT icon and the set temperature in the display window.
^ The system will operate with outside air in the vent function.
^ The A/C clutch will be turned OFF.

PANEL & FLOOR
Pressing the PANEL & FLOOR icon button will show the PANEL & FLOOR icon and the set temperature in the display window.
^ The system will distribute outside air equally between the A/C registers and the heater outlet floor duct with a small bleed to the A/C side window demister and hose and the windshield defroster hose nozzle.
^ The A/C clutch will operate if the ambient temperature is approximately 10° C (50° F) and above.

FLOOR
Pressing the FLOOR icon button will show the FLOOR icon and the set temperature in the display window.
^ The system will distribute outside air through the heater outlet floor duct with a small bleed to the A/C side window demister and hoses and the windshield defroster hose nozzle.
^ The A/C clutch will be turned OFF.

FLOOR & DEFROST
Pressing the FLOOR & DEFROST icon button will show the FLOOR and DEFROST icons and set temperature in the display window.
^ The system distributes outside air equally between the windshield defroster hose nozzle and the heat outlet floor duct with a small bleed out the A/C side window demister and hoses.
^ The A/C clutch will operate if the ambient temperature is approximately 10° C (50° F) and above.

F-DEF
Pressing the F-DEF icon button will show the defrost F-DEF icon and set temperature in the display window
^ The system distributes outside air to the windshield defroster hose nozzle and the heater outlet floor duct with a small bleed to the heater outlet floor ducts.
^ The A/C clutch will operate if the ambient temperature is approximately 10° C (50° F) and above.

- FAN +
The (- FAN +) rocker switch is used to turn OFF the AUTOMATIC blower indicator and provide manual control of the A/C blower motor speed.
^ The display will show FAN and a fan symbol.
^ Rock the button to the left and hold to lock the blower motor at its lowest speed.
^ Rock the button to the right and hold to lock the blower motor at its highest speed.
^ Press the AUTO button to resume automatic A/C blower motor control and remove the FAN and fan symbol from the display window.