The Refrigerant Cycle

For information regarding base refrigerant operation within the HVAC system, refer to the current Ford Web Based Technical Training courses. The diagram below shows the refrigerant system state in each component on this vehicle.

Some specific items to remember when working with this refrigerant 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 

Set the blower motor knob to any speed other than 0 to operate the system.

Controls and Compressor Operation 

All customer commands for the EMTC climate control system come through the HVAC control head.

A/C Request 

The HVAC control module sends the A/C request message to the GWM over the MS-CAN, then the GWM sends the request message to the PCM over the HS-CAN.

When the A/C request message is received by the PCM, the PCM engages the A/C clutch relay when all of the following conditions are met:

• The PCM does not detect excessively high or low refrigerant pressure from the A/C pressure transducer.
• The PCM does not detect engine coolant temperature excessively high.
• The PCM does not detect an ambient air temperature below approximately 0 deg.C (32 deg.F).
• The PCM does not detect a WOT condition present.
• The PCM does not receive a message from the BCM detecting an evaporator discharge air temperature below approximately 1 deg.C (33.8 deg.F).
• The PCM does not detect temperatures from the Mass Airflow/Intake Air Temperature sensor that does not correlate with other temperature sensor readings at ignition ON. (Most Mass Airflow (MAF) sensors have an integrated Intake Air Temperature (IAT) sensor).

The PCM monitors multiple temperature sensors for correlation (AAT CACT, CHT, ECT, IAT, IAT2, MAF, MAPT, TCBP, TCIPT as applicable). The PCM runs this logic after an engine off and a calibrated soak period, typically 6 to 8 hours. This soak period allows the Ambient Air Temperature (AAT) sensor (if equipped) and the other temperature sensors to stabilize and not differ by greater than a calibrated value, typically 18 deg.C (32.4 deg.F). If a sensor input is found to be reporting a temperature imbalance the PCM does not allow the A/C clutch to engage. For more information on PCM sensors, Refer to ENGINE CONTROLS - INTRODUCTION (EXCEPT DIESEL & HYBRID)

Compressor Clutch 

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 

All airflow from the blower motor passes through the evaporator core. Based on the climate control system temperature settings, the temperature door actuator directs airflow through or around the heater core as needed. The air distribution door actuator controls the airflow to the defrost, footwell or panel register vents. The air source is from either fresh air or recirculated passenger compartment air as determined by the air inlet door actuator position. The air inlet door actuator contains a reversible electric motor with no potentiometer and is either fully open or fully closed.

The air distribution door and temperature door actuators are DC 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 actuator's full range of movement.

The blower motor has 7 speeds controlled by the HVAC control module and a blower motor resistor.

Off 

When the system is off:

• the air inlet door closes.
• the blower motor is off.

Max A/C 

When MAX A/C mode is selected:

• the air inlet door closes allowing only recirculated air.
• the recirculated air indicator is illuminated (recirculated air forced on).
• the A/C button is illuminated.
• the A/C compressor operates if the outside air temperature is above approximately 2 deg.C (35 deg.F).

Panel 

When PANEL mode is selected:

• the mode doors direct airflow to the instrument panel registers.
• the recirculated air request button can be enabled.
• blended air temperature is available. The airflow temperature is only cooled below the outside air temperature when the A/C is commanded on.

Panel-Floor 

When PANEL-FLOOR mode is selected:

• 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.
• the recirculated air request button can be enabled.
• blended air temperature is available. The airflow temperature is only cooled below the outside air temperature when the A/C is commanded on.

Floor 

When FLOOR mode is selected:

• the mode doors direct airflow to the floor duct. A small amount of airflow from the defroster duct and side window demisters is present.
• the recirculated air request button can be enabled.
• blended air temperature is available. The airflow temperature is only cooled below the outside air temperature when the A/C is commanded on.

Floor-Defrost 

When FLOOR-DEFROST mode is selected:

• the mode doors direct airflow to the floor duct, the defroster duct and the side window demisters.
• the recirculated air request button can be enabled.
• blended air temperature is available. The airflow temperature is only cooled below the outside air temperature when the A/C is commanded on.

Defrost 

When DEFROST mode is selected:

• 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 recirculated air request button can not be enabled.
• the A/C is automatically commanded on and remains on until the system is either turned off or the airflow mode has changed and the A/C button is pressed.