The Refrigerant Cycle

For base operation regarding refrigerant operation within the HVAC system, please reference the current Ford Web Based Technical Training courses. The diagram below shows the states of the refrigerant in each component of the system for this vehicle. Please reference the diagram along with the training information for an understanding of the refrigerant cycle within this vehicle.

Some specific items to remember when working with this system:

• The PCM controls the A/C clutch relay.
• The evaporator temperature sensor monitors the temperature of the air that has passed through the evaporator core and sends a signal to the PCM. If the temperature of the evaporator core discharge air is low enough to cause the condensed water vapor to freeze, the A/C clutch is disengaged by the PCM.
• The line pressure is monitored so that A/C compressor operation is interrupted if the system pressure becomes too high or too low.
• The A/C compressor relief valve opens and vents refrigerant to relieve unusually high system pressure.

Thermostatic Expansion Valve (TXV) Type Refrigerant System State and Flow 

Courtesy of FORD MOTOR COMPANY

Item	Description
1	High pressure liquid
2	Low pressure liquid
3	High pressure vapor
4	Low pressure vapor

Control System Logic 

Climate Control System Network Communication 

The controls for the climate control system are in one or more locations depending on vehicle option content:

• HVAC control module (DATC)
• FDIM (part of the APIM

On vehicles with SYNC® system the touch screen and voice commands can be used for climate control inputs.

On vehicles without SYNC® system the customer preferences are input directly into the HVAC control module (DATC).

Controls and Compressor Operation 

Climate Control Commands - A/C Request 

Climate control commands are input through the HVAC control module. On vehicles equipped with SYNC® system inputs can also be commanded through voice commands or the touch screen. When the A/C is requested, the HVAC control module sends the message over the MS-CAN to the BCM. The BCM sends the A/C request through the HS-CAN to the PCM.

When an A/C request is received by the PCM, the PCM engages the A/C clutch relay when:

• the refrigerant pressure is not excessively high or low.
• the engine coolant temperature is not excessively high.
• the ambient air temperature is above approximately 0°C (32°F).
• a WOT condition is not present.
• the evaporator discharge air temperature is above approximately 1°C (33.8°F).

Compressor Clutch 

When A/C is requested and A/C line pressures allow, a ground is provided to the A/C clutch relay coil from the PCM, energizing the A/C clutch relay. When the PCM energizes the relay, voltage is supplied to the A/C compressor clutch field coil from the relay.

Air Handling 

Based on the climate control system temperature settings, the temperature door actuators direct airflow through the evaporator and heater cores as needed. The air distribution door actuators control the airflow to the defrost, floor or panel register vents. The air source is from outside air or recirculated passenger compartment air as determined by the air inlet door position.

The defrost, panel-floor, air inlet and temperature door actuators are stepper motors. There is no feedback circuit or potentiometer for these actuators. The pins labeled Door A, B, C and D are for the different phases (coils) of the motor. All the phases for a given motor are fed from A/Common power lead, the pin labeled Door Power and the HVAC control module controls each phase by turning a low side output on or off for the different phases. The motor turns, or steps, through a series of motions to position the actuator. The HVAC control module tracks the actuator positions by counting steps and periodically calibrates itself so it knows how many steps there are for the full range movement of the actuator. The HVAC control module sets Diagnostic Trouble Codes (DTCs) by monitoring the current flow through a given phase. If it sees too much current it identifies it as a short circuit. If it does not see any current it identifies it as an open circuit.

The HVAC control module sends a PWM signal to the blower motor control module to control the blower motor speed. The blower motor control module provides variable ground feed for the blower motor. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.

AUTO 

When AUTO is selected:

• the HVAC system operates in a manner to achieve and maintain the temperature set by the operator.
• the air inlet door is automatically controlled by the HVAC control module based on the temperature setting.
• the mode door is automatically controlled by the HVAC control module based on the temperature setting.
• the temperature blend door is automatically controlled by the HVAC control module based on the temperature setting.
• the A/C compressor is automatically controlled by the HVAC control module, based on the temperature setting. The A/C compressor does not operate if the outside temperature is below approximately 0°C (32°F).
• the blower motor speed is automatically controlled by the HVAC control module based on the temperature setting, but can be manually overridden.

Off 

When the system is OFF:

• the air inlet door closes, preventing outside air and allowing only recirculated air.
• the blower motor is off.

Max A/C 

When MAX A/C mode is selected:

• the air inlet door closes, preventing outside air and allowing only recirculated air.
• the recirculated air indicator is illuminated (recirculated air forced on).
• the mode doors direct airflow to the instrument panel registers.
• the temperature blend doors move to the full cool position. Air temperature can be manually overridden.
• the A/C button is illuminated.
• the A/C compressor operates if the outside temperature is above approximately 0°C (32°F).
• the blower motor is commanded to the highest speed. The blower motor speed is adjustable.

Panel 

When PANEL mode is selected:

• the recirculated air request button is enabled. If the recirculated air request button is selected (indicator ON), the air inlet door closes, preventing outside air from entering the passenger compartment. If the recirculated air request button is not selected (indicator OFF), the air inlet door opens, allowing only outside air into the passenger compartment.
• the mode doors direct airflow to the instrument panel registers.
• blended air temperature is available. The airflow temperature can only be cooled below the outside air temperature when the A/C is commanded on.
• the blower motor is on and the speed is adjustable.

Panel-Floor 

When PANEL-FLOOR mode is selected:

• the recirculated air request button is enabled. If the recirculated air request button is selected (indicator ON), the air inlet door closes, preventing outside air from entering the passenger compartment. If the recirculated air request button is not selected (indicator OFF), the air inlet door opens, allowing only outside air into the passenger compartment.
• the mode doors direct airflow to the floor duct and the instrument panel registers. A small amount of airflow from the side window demisters and defrost duct is present.
• blended air temperature is available. The airflow temperature can only be cooled below the outside air temperature when the A/C is commanded on.
• the blower motor is on and the speed is adjustable.

Floor 

When FLOOR mode is selected:

• the recirculated air request button is enabled. If the recirculated air request button is selected (indicator ON), the air inlet door closes, preventing outside air from entering the passenger compartment. If the recirculated air request button is not selected (indicator OFF), the air inlet door opens, allowing only outside air into the passenger compartment.
• the mode doors direct airflow to the floor duct. A small amount of airflow from the defroster duct and side window demisters is present.
• blended air temperature is available. The airflow temperature can only be cooled below the outside air temperature when the A/C is commanded on.
• the blower motor is on and the speed is adjustable.

Floor-Defrost 

When FLOOR-DEFROST mode is selected:

• the recirculated air request button is enabled. If the recirculated air request button is selected (indicator ON), the air inlet door closes, preventing outside air from entering the passenger compartment. If the recirculated air request button is not selected (indicator OFF), the air inlet door opens, allowing only outside air into the passenger compartment.
• the mode doors direct airflow to the floor duct, the defroster duct and the side window demisters.
• blended air temperature is available. The airflow temperature can only be cooled below the outside air temperature when the A/C is commanded on.
• the blower motor is on and the speed is adjustable.

Defrost 

When DEFROST is selected:

• the recirculated air request button is disabled. The air inlet door opens, allowing only outside air into the passenger compartment.
• the mode doors direct airflow to the defroster duct and side window demisters. A small amount of airflow from the floor duct is present.
• the A/C is turned on in DEFROST. The A/C compressor operates as long as the outside temperature is above approximately 0°C (32°F).
• blended air temperature is available.
• the blower motor is on and the speed is adjustable.

MyFord Touch® (if equipped) 

The MyFord Touch® feature can be used to store and recall the driver's preset temperature. This feature is provided so this temperature can be quickly adjusted to a frequently used setting with a single button press. For additional information about MyFord Touch®, refer to the Owner's Literature.