HVAC System - Control Components Ford Crown Victoria II

Electronic Automatic Temperature Control

With the use of a microcontroller, the climate control assembly (EATC module) analyzes input from the following major sources

1. temperature, function and blower selection (made by the vehicle occupants)
2. in-vehicle temperature sensor
3. ambient temperature sensor
4. sunload sensor
5. vehicle speed sensor
6. engine coolant temperature sensor
7. evaporator discharge air temperature sensor

Using these inputs, the microcontroller determines the correct conditions for the following outputs

1. A/C clutch engagement
2. blower speed
3. air temperature blend door position
4. floor/panel door position
5. panel/defrost door position
6. air inlet duct door position

Climate Control Assembly

The electronic automatic temperature control (EATC) module, located in the instrument panel, has the following features

1. a blower speed override control for manual input.
2. a vacuum fluorescent display for displaying set temperature, ambient temperature, function and diagnostic trouble codes (DTCs).
3. an On-Board Diagnostic (OBD) feature to supply the technician with diagnostic trouble codes (DTCs). These DTCs direct the technician to the inoperative component.

Steering Wheel Audio/Climate Control Switch

The steering wheel audio/climate control switch, located on the right side of the steering wheel, allows the driver to adjust the passenger compartment temperature setting and manually override the blower motor speed setting. For removal and installation of the steering wheel audio/climate control switch, refer to STEERING WHEEL AUDIO CONTROLS .

Evaporator Discharge Air Temperature Sensor

The PCM (12A696) determines A/C compressor clutch cycling based on input from the evaporator discharge air temperature sensor (19C734). The evaporator air discharge temperature sensor

1. maintains evaporator core temperature, and prevents icing of the evaporator core (19860) by disengaging the A/C compressor clutch when the evaporator discharge air temperature falls below a preset level, and engaging the A/C compressor clutch when the discharge air temperature rises above a preset level. For information regarding operating temperature specifications, refer to «CLIMATE CONTROL SYSTEM-GENERAL INFORMATION»(/ford/crown-victoria/ii-1997-2011/remont/general-servicing-all-makes/#hvac-control-system-general-information)
2. contains a thermistor which receives a reference voltage from the PCM. The thermistor then varies the resistance to the reference voltage based on the evaporator discharge air temperature. The resulting voltage is returned to the PCM where it is interpreted as an evaporator air discharge temperature reading.
3. is located in the evaporator core housing just downstream of the evaporator airflow.

A/C Ambient Air Temperature Sensor

The A/C ambient air temperature sensor

1. Located in front of the A/C condenser core near the center of the vehicle.
2. contains a thermistor which measures the temperature of outside air as a resistance and sends that reading to the electronic automatic temperature control assembly.

In-Car Temperature Sensor

The in-vehicle temperature sensor operates in the following manner

1. A thermistor in the in-vehicle temperature sensor measures air temperature inside the passenger compartment.
2. An automatic temperature control sensor hose and elbow is connected between the A/C evaporator housing and the in-vehicle temperature sensor.
3. The automatic temperature control sensor hose and elbow takes air from the A/C evaporator housing air stream to create a suction in the in-vehicle temperature sensor.
4. The suction draws in-vehicle air into the in-vehicle temperature sensor and across the thermistor.

A/C Sunload Sensor

The A/C sunload sensor

1. is located on the top RH side of the instrument panel above the glove compartment.
2. contains a photovoltaic diode that is sensitive to light.
3. has some unspecified resistance across the terminals depending upon the amount of light reaching the photovoltaic diode; therefore the only test that can be performed is for an internal short circuit.

A/C Blower Motor Speed Control

The A/C blower motor speed control is located on the A/C evaporator housing, in the engine compartment.

1. The function of the A/C blower motor speed control is to convert low power signals from the electronic automatic temperature control module to a high current, variable ground feed for the blower motor.
2. Blower motor speed is infinitely variable and is controlled by the electronic automatic temperature control module software.
3. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.

A/C Electronic Blend Door Actuator

The A/C electronic blend door actuator is located on the top of the plenum housing.

1. Its function is to move the air temperature blend door on command from the control assembly.
2. The A/C electronic blend door actuator contains a reversible electric motor and a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the air temperature blend door.
3. A 5 volt signal is applied to the ends of the potentiometer. The voltage available at the wiper indicates the position of the potentiometer. The expressed value of the actuator wiper voltage is sent to the electronic automatic temperature control module and is matched with the wiper voltage of the module potentiometer. The control module then drives the actuator motor in the direction necessary to make the actuator wiper voltage agree with the control module wiper voltage.

Vacuum Control Motors

Vacuum control motors are used to move the floor/panel and panel/defrost doors.

Manual Climate Control

The manual climate control system heats or cools the vehicle interior depending on the function selector switch position and the temperature selected. The function selector position determines heating or cooling and air distribution. The temperature blend control setting determines air temperature.

The manual climate control system components are used to select

1. air inlet source (outside or recirculated).
2. blower motor speed.
3. discharge air temperature (temperature blend).
4. discharge air location (defrost, panel, floor).
5. A/C compressor clutch operation.

The climate control assembly has three system controls

1. The A/C heater function selector switch combines a vacuum selector valve with two electrical switches to supply battery voltage (B+) to the A/C clutch circuit and the blower motor speed control circuit.
2. Temperature selection is accomplished with a potentiometer connected to the electric blend door. Movement of the control knob from COOL (Blue) to WARM (Red) causes a corresponding movement on the air temperature blend door and determines the temperature that the system will maintain.
3. The blower motor switch controls blower motor speed by adding or bypassing resistors in the heater blower motor switch resistor.

The PCM (12A696) determines A/C compressor clutch cycling based on input from the evaporator discharge air temperature sensor (19C734). The evaporator air discharge temperature sensor

1. maintains evaporator core temperature, and prevents icing of the evaporator core (19860) by disengaging the A/C compressor clutch when the evaporator discharge air temperature falls below a preset level, and engaging the A/C compressor clutch when the discharge air temperature rises above a preset level. For information regarding operating temperature specifications, refer to «CLIMATE CONTROL SYSTEM-GENERAL INFORMATION»(/ford/crown-victoria/ii-1997-2011/remont/general-servicing-all-makes/#hvac-control-system-general-information) .
2. contains a thermistor which receives a reference voltage from the PCM. The thermistor then varies the resistance to the reference voltage based on the evaporator discharge air temperature. The resulting voltage is returned to the PCM where it is interpreted as an evaporator air discharge temperature reading.
3. is located in the evaporator core housing just downstream of the evaporator airflow.

Blower Motor Switch Resistor

The heater blower motor switch resistor has the following features

1. The assembly is located in the engine compartment on the evaporator housing toward the center of the vehicle.
2. Three resistor elements are mounted on the resistor board to provide four blower motor speeds.
3. Depending on the heater blower motor switch position, series resistance is added or bypassed in the A/C blower motor circuit to decrease or increase A/C blower motor speed.
4. A device to prevent overheating (thermal limiter) will open the resistor coil when the temperature reaches 121°C (250°F) interrupting the blower motor operation in all speeds except HI.
5. The thermal limiter cannot be reset and is not serviceable.

The A/C electronic blend door actuator is located on the top of the plenum housing.

1. Its function is to move the air temperature blend door on command from the temperature control switch.
2. The A/C electronic blend door actuator contains a reversible electric motor and a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the air temperature blend door.

Vacuum control motors are used to move the floor/panel and panel/defrost doors.

Refer to CLIMATE CONTROL SYSTEM-GENERAL INFORMATION .

Scheme 33

Scheme 34

Scheme 35

Scheme 36

1. Remove the finish panel.
2. Disconnect the connector.
3. Remove the screws and pull the electronic automatic temperature control (EATC) module from the instrument panel.
4. Remove the climate control assembly. Remove the nuts and the vacuum harness. Disconnect the wire harness connectors and remove the EATC module.
5. To install, reverse the removal procedure.

Scheme 37

Scheme 38

Scheme 39

Scheme 40

1. Remove the finish panel.
2. Disconnect the connector.
3. Remove the climate control head. Remove the screws. Remove the climate control head.
4. Disconnect the climate control assembly. Disconnect the electrical connectors. Disconnect the vacuum line connector.
5. To install, reverse the removal procedure.

Scheme 41

1. Remove the climate control assembly. For additional information, refer to «CLIMATE CONTROL ASSEMBLY-MANUAL A/C»(/ford/crown-victoria/ii-1997-2011/remont/automatic-hvac-system/#hvac-system-control-components) .
2. Pull and remove the blower motor switch knob.
3. Remove the blower motor switch. Release the tabs. Remove the blower motor switch.
4. To install, reverse the removal procedure.

Scheme 42

1. Remove the climate control assembly. For additional information, refer to «CLIMATE CONTROL ASSEMBLY-MANUAL A/C»(/ford/crown-victoria/ii-1997-2011/remont/automatic-hvac-system/#hvac-system-control-components) .
2. Pull and remove the temperature control switch knob.
3. Remove the temperature control switch. Remove the screw. Rotate and remove the temperature control switch.
4. To install, reverse the removal procedure.

Scheme 43

1. Remove the climate control assembly. For additional information, refer to «CLIMATE CONTROL ASSEMBLY-MANUAL A/C»(/ford/crown-victoria/ii-1997-2011/remont/automatic-hvac-system/#hvac-system-control-components) .
2. Pull and remove the function selector switch knob.
3. Remove the function selector switch. Release the tabs. Remove the function selector switch.
4. To install, reverse the removal procedure.

Scheme 44

Scheme 45

Scheme 46

1. Remove the upper radiator sight shield.
2. Disconnect the electrical connector.
3. Remove the ambient air temperature sensor.
4. To install, reverse the removal procedure.

Scheme 47

Scheme 48

Scheme 49

Scheme 50

Scheme 51

Scheme 52

1. Remove the finish panel.
2. Disconnect the connector.
3. Remove the screws and pull the control assembly away from the instrument panel.
4. Remove the screws and position the in-vehicle temperature sensor to access the connector.
5. Disconnect the connector.
6. Disconnect the hose and remove the in-vehicle temperature sensor.
7. To install, reverse the removal procedure.

Scheme 53

Scheme 54

Scheme 55

1. Remove the instrument panel. For additional information, refer to «INSTRUMENT PANEL»(/ford/crown-victoria/ii-1997-2011/remont/gauges-instrument-panels/#instrument-panel-and-console) .
2. Disconnect the connector.
3. Remove the four screws.
4. Remove the temperature blend door actuator.
5. To install, reverse the removal procedure.

Scheme 56

Scheme 57

Scheme 58

Scheme 59

1. Drain the engine coolant. For additional information, refer to «DRAINING»(/ford/crown-victoria/ii-1997-2011/remont/cooling-system-mechanical/#engine-cooling-system__draining) .
2. Remove the nuts and position the vapor management valve (VMV) aside.
3. Release the clamps and disconnect the heater hoses from the heater core.
4. Release the clamp and remove the heater hose.
5. Remove the blower motor speed control. Disconnect the electrical connector. Remove the screws. Remove the blower motor speed control.
6. To install, reverse the removal procedure.
7. Fill the engine cooling system. For additional information, refer to «COOLING SYSTEM DRAINING, FILLING AND BLEEDING»(/ford/crown-victoria/ii-1997-2011/remont/cooling-system-mechanical/#engine-cooling-system) .

Scheme 60

Scheme 61

Scheme 62

Scheme 63

1. Remove the pin-type retainers and the instrument panel lower insulator.
2. Disconnect the vacuum connector.
3. Remove the control arm clip and the spring.
4. Remove the nuts and the air inlet door vacuum control motor.
5. To install, reverse the removal procedure.

Scheme 64

Scheme 65

Scheme 66

Scheme 67

Scheme 68

Scheme 69

Scheme 70

Scheme 71

Scheme 72

1. Disconnect the battery ground cable. For additional information, refer to «BATTERY DISCONNECT»(/ford/crown-victoria/ii-1997-2011/remont/charging-system/#battery-mounting-and-cables__battery-disconnect) .
2. Remove the LH lower dash insulator panel and disconnect the lamp.
3. Remove the two pin-type retainers and remove the fill panel.
4. Remove the screws.
5. Detach the vacuum line.
6. Remove the lighting module. Remove the screws. Disengage the clip. Remove the lighting module.
7. Disconnect the electrical connectors.
8. Remove the screws and the bracket.
9. Remove the floor/defrost door vacuum control motor. Remove the clip. Remove the nuts. Remove the floor/defrost door vacuum control motor.
10. Disconnect the vacuum lines.
11. To install, reverse the removal procedure.

Scheme 73

Scheme 74

1. Remove the instrument panel. For additional information, refer to «INSTRUMENT PANEL»(/ford/crown-victoria/ii-1997-2011/remont/gauges-instrument-panels/#instrument-panel-and-console) .
2. Reach through the door opening and remove the pin.
3. Disconnect the panel door vacuum control motor vacuum line.
4. Remove the screws and remove the panel door vacuum control motor.
5. To install, reverse the removal procedure.

Scheme 75

Scheme 76

Scheme 77

1. Remove the relay module.
2. Disconnect the vacuum hose.
3. Raise the vehicle. For additional information, refer to «JACKING & LIFTING»(/ford/crown-victoria/ii-1997-2011/remont/hoistjack/#jacking-lifting) .
4. From inside the LH wheel well, remove the nuts.
5. Remove the vacuum reservoir tank.
6. To install, reverse the removal procedure.

See also:
• STEERING WHEEL AUDIO CONTROLS
• CLIMATE CONTROL SYSTEM-GENERAL INFORMATION
• INSTRUMENT PANEL
• DRAINING
• COOLING SYSTEM DRAINING, FILLING AND BLEEDING
• BATTERY DISCONNECT
• JACKING & LIFTING
• CLIMATE CONTROL ASSEMBLY-MANUAL A/C