Electronic Climate Control

The Electronic Automatic Temperature Control (EATC) system is an Option on Crown Victoria and Grand Marquis vehicles.

With the use of a microcomputer, the control assembly analyzes input from the following major sources:
^ temperature, function and blower selections (made by the vehicle occupants)
^ in-vehicle temperature
^ ambient temperature
^ A/C sunload sensor
^ Powertrain Control Module (PCM)





Using these inputs, the microcomputer determines the correct conditions for the following six outputs:
^ A/C clutch engagement
^ blower speed
^ A/C air temperature control door position
^ [1][2]heater air damper door position
^ [1][2]windshield defroster door position
^ heater and A/C air inlet duct door position

An A/C 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 A/C 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 A/C blower motor speed control.





^ The A/C blower motor speed control reacts to the low power signal from the control assembly to provide the high power signal required to drive the blower motor. The following system response chart shows the control assembly response to the function selections.

An On-Board Diagnostic feature has been included in the control assembly to supply the technician with Diagnostic Trouble Codes (DTCs). These codes direct the technician to the inoperative component. Inspection and Verification under Diagnosis and Testing. Initial Inspection and Diagnostic Overview

System Operation
The system automatically maintains the temperature selected for driving comfort and regulates the airflow between the:
^ A/C register.
^ heater outlet floor duct.
^ demister nozzle and duct.
^ A/C side window demister and hose.

The system also provides the option of manually overriding the blower speed and 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 be displayed at any time by momentarily pressing the OUTSIDE TEMP button. The outside temperature will then be displayed until the button is pressed again.

For optimum automatic operation, the system should be in AUTO 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.

AUTOMATIC
Press the AUTOMATIC button to turn the system ON for fully automatic operation. When functioning automatically, the digital display window will show AUTO and the set temperature. The system will maintain this temperature by controlling airflow direction (functional setting), airflow quantity (fan speed) and discharge temperature required for comfort.
^ When heating is required, airflow will automatically be directed through heater outlet floor ducts and A/C side window demister and hoses with a small amount of air through demister nozzle and duct.
^ During cool weather when the engine coolant is below approximately 50°C (122°F) and heat is required, the airflow will be directed to the defroster outlets at low blower speed. When engine coolant temperature reaches 50°C (122°F) or after 3-1/2 minutes (whichever occurs first), the blower speed will increase and airflow will shift to the floor.
^ When cooling is required, airflow will be directed through instrument panel registers. A/C registers can be adjusted for optimum comfort.
^ When maximum cooling is required, the system will automatically operate with recirculated air for rapid cool-down and automatically change to outside air as the passenger compartment interior approaches the selected temperature.
^ In moderate conditions, the system will automatically operate with airflow directed through heater outlet floor duct and through demister nozzle and duct at a moderate temperature and fan speed.

OFF
Pressing the OFF button:
^ will turn the system oft.
^ leaves the digital display window blank (dark) unless OUTSIDE TEMP has been selected.





Digital Display Window
The digital display window will indicate one of three displays depending upon the manual selection:
^ selected comfort temperature
^ outside temperature
^ function selected

Warmer (Red) Button
Press the red button to raise the temperature setting.
^ Press the button once to 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.

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

OUTSIDE TEMP
Press this button to display the outside temperature.
^ The outside temperature will be displayed until the button is pressed again.
^ If the set temperature is changed while the outside temperature is selected, the set temperature will be displayed for four seconds and then revert back to the 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. Depressing 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 control assembly. Each affects system operation as follows:

MAX A/C
Depressing the MAX A/C button will show MAX A/C and the set temperature in the display window.
^ 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.

NORM A/C
Depressing the NORM A/C button will show A/C and the set temperature in the display window.
^ The system will draw air from outside the vehicle.
^ The A/C clutch will operate if the ambient temperature is approximately 10°C (50°F).

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

FLOOR
Pressing the FLOOR button will show FLR 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 demister nozzle and duct.
^ The A/C clutch will be turned OFF.

FLR-DEF
Pressing the FLR-DEF button will show FLOOR, the defrost symbol and set temperature in the display window.
^ The system distributes outside air equally between the demister nozzle and duct and the heater 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.

DEF
Pressing the DEFROST button will show the defrost symbol and set temperature in the display window.
^ The system distributes outside air to the demister nozzle and duct and the A/C side window demister and hose 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.

Blower Speed Override Thumbwheel
Rotate the blower speed override thumbwheel more than 10 degrees 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 icon.
^ Rotating the wheel fully down against its lower stop locks the A/C blower motor at its lowest speed.
^ Rotating the wheel fully up against the stop locks the blower at its highest speed. Press the AUTOMATIC button to resume automatic A/C blower motor control and remove the FAN and icon from the display window.