System Operation
System Diagram
Item | Description |
---|---|
1 | GWM |
2 | Ambient Air Temperature (AAT) sensor |
3 | PCM |
4 | A/C pressure transducer |
5 | A/C clutch relay |
6 | A/C compressor clutch field coil |
7 | HVAC Control Module |
8 | Air distribution door actuator |
9 | Temperature door actuator |
10 | Air inlet door actuator |
11 | Blower motor relay |
12 | Blower motor control module |
13 | Externally Controlled Variable Displacement Compressor (EVDC) |
14 | In-vehicle temperature and humidity sensor |
15 | Driver side footwell air discharge temperature sensor |
16 | Driver side register air discharge temperature sensor |
17 | Evaporator temperature sensor |
18 | Sunload sensor |
19 | APIM |
20 | Ambient air quality sensor (if equipped) |
paragraph
Network Message Charts
Module Network Input Messages - IPC
Broadcast Message | Originating Module | Message Purpose |
---|---|---|
Climate control status | HVAC Control Module | This message contains the HVAC mode status for the mode indicators. |
Module Network Input Messages - PCM
Broadcast Message | Originating Module | Message Purpose |
---|---|---|
A/C request (gateway) | HVAC Control Module | This message requests the A/C compressor clutch to be engaged. |
Module Network Input Messages - HVAC Control Module
Broadcast Message | Originating Module | Message Purpose |
---|---|---|
Climate control requests (gateway) | BCM | This message contains all climate control system controls requests except blower motor speed. |
Remote start status | BCM | This message contains the climate control system controls request for remote start. |
A/C clutch status | PCM | This message contains the A/C compressor clutch status. |
Ambient air temperature | PCM | This message contains raw value from the ambient air temperature sensor. |
The Refrigerant Cycle
For information regarding basic HVAC (heating, ventilation and air conditioning) system refrigerant operation, refer to the current Ford Web Based Technical Training courses. The following diagram shows the refrigerant system state in each component.
The following are characteristics of the EATC system:
Thermostatic Expansion Valve (TXV) Type Refrigerant System
Item | Description |
---|---|
1 | High pressure liquid |
2 | Low pressure liquid |
3 | High pressure vapor |
4 | Low pressure vapor |
Control System Logic
When the customer directly inputs an A/C request into the HVAC control module, the module sends the request to the GWM over the MS-CAN . The GWM relays the request to the PCM over the HS-CAN1 . The PCM controls the A/C clutch relay.
A/C Request
When the A/C is requested, the HVAC control module sends the message over the MS-CAN to the GWM . The GWM 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 all of the following conditions are met:
Compressor control and the evaporator temperature are a function of many parameters, not just a straight on/off, to avoid freezing the evaporator. The PCM monitors multiple temperature sensors for correlation including, but not limited to, AAT, CACT, CHT, ECT, IAT, IAT2, MAF, MAPT, TCB and TCIPT Parameter Identifications (PIDs) (as applicable). The PCM runs this logic after an engine off and a calibrated soak period of 6 to 8 hours. This soak period allows the Ambient Air Temperature (AAT) sensor and the other temperature sensors to stabilize and not differ by greater than a calibrated value, typically 18ºC (32.4ºF). If a temperature sensor input is found to be reporting a temperature imbalance the PCM does not allow the A/C clutch to engage.
The PCM monitors the discharge pressure measured by the A/C pressure transducer. The PCM interrupts A/C compressor operation in the event the A/C pressure transducer indicates high system discharge pressures. It is also used to sense low charge conditions. If the pressure is below a predetermined value for a given ambient temperature, the PCM does not allow the A/C clutch to engage
The HVAC control module adjusts the system based on cabin temperature. If equipped with the in-vehicle and humidity sensor, the HVAC control module also adjusts the air inlet door depending on the humidity measured by the in-vehicle temperature and humidity sensor. If the vehicle cabin becomes too humid and recirculated air is selected, the HVAC control module adjusts the air inlet door to allow more fresh air. When the humidity level drops, it adjusts back to partial recirculated air.
Heating and Ventilation
The heating and ventilation system:
The heating and ventilation system uses a reheat method to provide conditioned air to the passenger compartment. Temperature blending is controlled by the temperature doors, which regulate the amount of air that flows through and around the heater core, where it is then mixed and distributed. All airflow from the blower motor passes through the A/C evaporator core.
Vehicles built prior to 2022 model year, are equipped with a cabin heater coolant pump for Auto Start-Stop conditions. The pump is activated by the PCM to maintain the cabin temperature if required when in an Auto Start-Stop condition.
Air Handling
There are 3 door actuators that control the air flow into the passenger compartment:
All of the door actuators contain a reversible electric motor and a potentiometer. The potentiometer circuit consists of a 5-volt reference signal connected to one end of a variable resistor, and a signal ground connected to the other. A signal circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal to the HVAC control module from the contact wiper indicates the actuator door position. The HVAC control module powers the actuator motors to move the doors to the desired positions. The desired door positions are calculated by the HVAC control module based on the set temperature, in-vehicle temperature (if equipped the in-vehicle temperature and humidity sensor), and ambient air temperature.
When an airflow mode, desired temperature, fresh air, or recirculation mode is selected, the HVAC control module moves the actuator motor in the desired direction.
The HVAC control module sends a PWM signal to the blower motor control module to regulate the blower speed as necessary. The blower motor control module provides variable ground feed for the blower motor based on the input from the HVAC control module. A delay function provides a gradual increase or decrease in blower motor speed under all conditions
Air Flow Strategy For Anti Fogging
This vehicle is equipped with an anti fogging feature known as enhanced windshield anti fogging strategy (EWAFS). This feature is based off the input data that is sent from the in-vehicle temperature and humidity sensor that is mounted near the center top of the windshield typically under the IPMA cover. The in-vehicle temperature and humidity sensor is hard wired to the HVAC module and supplies the vehicles humidity and temperature to the HVAC module. The module uses that data automatically to adjust the airflow in the cabin to prevent the windshield from fogging up. Below are the feature details and climate control operation based on the vehicles climate control system.
Background Strategy Operations | ||
Background Feature Details | Single Zone Manual | Dual Zone/Single Zone Auto |
To prevent window fogging, recirculated air cannot be switched on when MAX Defrost is on. | X | X |
In certain conditions (i.e. Max Defrost), the A/C compressor may continue to operate even though the A/C button is off. | X | X |
In certain conditions, the A/C button may turn on and off automatically based on the temperature setting and/or the current conditions. | X | X |
Recirculated air may turn off automatically (or be prevented from turning on) in all airflow modes except MAX A/C to reduce risk of fogging. Recirculated air may also turn on and off automatically in various airflow modes in order to improve heating or cooling efficiency. | X | X |
Whenever the blower motor speed is automatically controlled, all of the blower indicators turn off. | - | X |
When Auto operation is switched on the air distribution, A/C operation, and outside or recirculated air will also be automatically controlled to heat or cool the vehicle in order to maintain the selected temperature. Under high humidity conditions, automatic operation will also take action to reduce the risk of window fogging by automatically engaging the A/C compressor, increasing blower motor speed, and/or directing more air to the windshield. | - | X |
AUTO
When AUTO is selected:
OFF
When the system is OFF:
Max A/C
When MAX A/C mode is selected:
PANEL
When PANEL mode is selected:
PANEL-FLOOR
When PANEL-FLOOR mode is selected:
FLOOR
When FLOOR is selected:
FLOOR-DEFROST
When FLOOR-DEFROST is selected:
DEFROST
When DEFROST is selected:
Remote Start
Remote start is an optional feature available on this vehicle. In addition to being able to start the vehicle remotely, the remote start feature also utilizes other vehicle systems to increase the level of comfort to the vehicle occupants upon entering the vehicle. Additional information on the remote start feature and the other vehicle systems, refer to Owner's Literature.
When the factory remote start feature is used, the EATC system runs at the setting it was set to when the vehicle was last turned off. Set the climate control to operate using the last climate control settings through the information display setting: Remote Start > Climate Control > Heater–A/C > Last Settings. The climate control system automatically uses the settings last selected before the vehicle was turned off. Refer to the Owner's Literature for more information.
Component Description
Component Description
Heating Ventilation Air Conditioning (HVAC) Control Module - Electronic Automatic Temperature Control (EATC)
The EATC HVAC control module is on the MS-CAN and sets DTCs. A/C requests are sent to the GWM and then to the PCM via the HS-CAN1 .
The temperature control switch adjusts the discharge air temperature. Movement of the temperature knob from cool to warm causes a corresponding movement of the temperature door. The position of the temperature door determines the discharge air temperature. The temperature control selector is an integral part of the HVAC control module and cannot be serviced separately.
The airflow mode setting adjusts the discharge air outlet location. Each airflow mode selector icon causes a corresponding movement of the airflow mode doors and determines the discharge air outlet location. The airflow mode selector knob is an integral part of the HVAC control module and cannot be serviced separately.
The A/C button determines A/C compressor operation, except when the temperature selector is set to MAX A/C or the airflow mode selector is in Defrost mode. The A/C button is an integral part of the HVAC control module and cannot be serviced separately.
The recirculated air request button can be activated in any mode except Defrost. In MAX A/C mode the recirculated air indicator is illuminated (recirculated air forced on). The recirculated air request button is an integral part of the HVAC control module and cannot be serviced separately.
Ambient Air Quality Sensor (if equipped)
The ambient air quality sensor is an input to the HVAC control module. When pollution and bad odors coming from the external environment are detected, the air inlet door automatically closes.
Ambient Air Temperature (AAT) Sensor
The Ambient Air Temperature (AAT) sensor is an input to the PCM . If the outside air temperature is below approximately 0°C (32°F), the PCM does not allow the A/C compressor clutch to engage.
The PCM sends raw ambient air temperature data to the HVAC control module. The HVAC control module filters the raw data, sends it to the APIM and the touchscreen displays the outside temperature.
After replacing an Ambient Air Temperature (AAT) sensor, the sensor
data must be reset by following the menu prompts on the FDRS scan tool.
Refer
to: Reset the Outside Air Temperature Sensor Learned Values (412-00
Climate Control System - General Information, General Procedures).
A/C Compressor Clutch Assembly
When battery voltage is applied to the A/C compressor clutch field coil, the clutch disc and hub assembly is drawn toward the A/C clutch pulley. The magnetic force locks the clutch disc and hub assembly and the A/C clutch pulley together as one unit, causing the compressor shaft to rotate with the engine. When battery voltage is removed from the A/C compressor clutch field coil, springs in the clutch disc and hub assembly move the clutch disc away from the A/C clutch pulley.
An A/C clutch diode is integrated into the coil for A/C clutch field coil circuit spike suppression.
Internal Heat Exchanger (IHX)
The evaporator inlet and outlet manifold incorporates the Internal Heat Exchanger (IHX) and is serviced as an assembly. The Internal Heat Exchanger (IHX) combines a section of the A/C suction and liquid refrigerant lines into one component. It uses the cold vapor from the evaporator to cool the hot liquid from the condenser before it enters the Thermostatic Expansion Valve (TXV). After the Thermostatic Expansion Valve (TXV), more liquid refrigerant is available for absorbing heat in the evaporator. The result is an increase in cooling and operating efficiency of the HVAC system.
Externally Controlled Variable Displacement Compressor
NOTE: Proper Air Conditioning (A/C) system diagnosis on a vehicle's compressor is dependent on correct refrigerant system charge and tested in ambient temperatures above 21.1°C (70°F).
Variable displacement compressor internals are similar to fixed displacement compressors. The pistons are placed around an angled plate (swash plate) and are pushed back and forth as the plate rotates. Variable displacement compressors vary the swash plate angle to allow piston displacement to vary from 5% (default) to 100% of full capacity to meet cooling demand.
The externally controlled variable displacement compressor has the following characteristics:
The piston displacement of the externally controlled variable displacement compressor is controlled by a PWM signal from the PCM which electronically drives the control valve. The control valve drives the crankcase pressure and thus the swash plate angle. The externally controlled variable displacement compressor achieves precise cooling capability based on the cabin temperature and driving conditions, resulting in the target evaporator core temperature. The target evaporator core temperature range for the EATC system is 3-8°C (37.4-46.4°F); 3-5°C (37.4-41°F) for the EMTC system.
The PCM pulse width modulates the ground to the externally controlled variable displacement compressor control valve to change the displacement of the A/C compressor by changing the swash plate angle based on the following items:
Thermostatic Expansion Valve (TXV)
The Thermostatic Expansion Valve (TXV) is located at the evaporator core inlet and outlet tubes at the center rear of the engine compartment. The Thermostatic Expansion Valve (TXV) provides a restriction to the flow of refrigerant and separates the low-pressure and high-pressure sides of the refrigerant system. Refrigerant entering and exiting the evaporator core passes through the Thermostatic Expansion Valve (TXV) through 2 separate flow paths. An internal temperature sensing bulb senses the temperature of the refrigerant flowing out of the evaporator core and adjusts an internal pin-type valve to meter the refrigerant flow into the evaporator core. The internal pin-type valve decreases the amount of refrigerant entering the evaporator core at lower temperatures and increases the amount of refrigerant entering the evaporator core at higher temperatures.
A/C Condenser
The A/C condenser is an aluminum fin-and-tube design heat exchanger. It cools compressed refrigerant gas by allowing air to pass over fins and tubes to extract heat, and condenses gas to liquid refrigerant as it is cooled.
Receiver Drier
The receiver drier stores high-pressure liquid and the desiccant bag mounted inside the receiver drier removes any retained moisture from the refrigerant.
For 2.5L Duratec engine equipped vehicles, the receiver drier is incorporated into the LH side of the A/C condenser. The receiver drier element is a separate component and can be removed and installed with the A/C condenser in the vehicle.
For 1.5L and 2.0L EcoBoost engine equipped vehicles, the receiver drier is externally mounted to the LH side of the condenser core.
Blower Motor Control Module
The blower motor and the blower motor speed control are combined into one assembly called the blower motor control module. The blower motor pulls air from the air inlet and forces it into the climate control housing and the plenum chamber where it is mixed and distributed. The blower motor speed control uses a PWM signal from the HVAC Control Module to determine the desired blower speed and varies the ground feed for the blower motor to control the speed.
Evaporator Core
The evaporator core is an aluminum tube and fin type and is located in the climate control housing. A mixture of liquid refrigerant and oil enters the evaporator core through the evaporator core inlet tube and continues out of the evaporator core through the evaporator core outlet tube as a vapor. During A/C compressor operation, airflow from the blower motor is cooled and dehumidified as it flows through the evaporator core fins.
Heater Core
The heater core consists of fins and tubes arranged to extract heat from the engine coolant and transfer it to air passing through the heater core.
Climate Control Housing
The climate control housing directs airflow from the blower motor through the evaporator core and heater core. All airflow from the blower motor passes through the evaporator core. The airflow is then directed through or around the heater core by the temperature doors. After passing through the heater core, the airflow is distributed to the selected outlet by the airflow mode doors.
Cabin Heater Coolant Pump (If equipped)
The cabin heater coolant pump is utilized to circulate coolant though the vehicles cooling system based on certain vehicle demands. During low engine speeds the pump increases heater core flow that the main engine coolant pump provides. The specific RPM threshold varies based on the ambient and coolant temperatures. It also supplies coolant flow during an auto start - stop condition to maintain the cabin temperature when the cabin heat is turned on. The pump also turns on in response to high engine oil temperatures and increases the flow through the oil cooler to reduce the oil temperature. The pump is commanded on by the PCM .
A/C Pressure Transducer
The PCM monitors the discharge pressure measured by the A/C pressure transducer. As the refrigerant pressure changes, the resistance of the A/C pressure transducer changes. It is not necessary to recover the refrigerant before removing the A/C pressure transducer.
A 5-volt reference voltage is supplied to the A/C pressure transducer from the PCM . The A/C pressure transducer receives a ground from the PCM . The A/C pressure transducer then sends a voltage to the PCM to indicate the A/C refrigerant pressure.
In-Vehicle Temperature and Humidity Sensor (if equipped)
The in-vehicle temperature and humidity sensor is an input to the HVAC control module. The in-vehicle temperature and humidity sensor contains a thermistor and a sensing element which separately measures the in-vehicle air temperature and the humidity. The in-vehicle temperature and humidity sensor has an electric fan within the sensor that draws in-vehicle air across the two sensing elements. The HVAC control module may adjust the air inlet door based on the in-vehicle temperature and humidity sensor information to maintain the desired humidity of the passenger cabin air.
Sunload Sensor
The sunload sensor supplies information to the HVAC control module indicating the intensity of the sun on the vehicle. The HVAC control module compensates high sun load with higher blower speed and reduced discharge temperatures.
Air Discharge Temperature Sensors
There are 2 air discharge temperature sensors in the EATC system:
The air discharge temperature sensors contain a thermistor and are inputs to the HVAC control module. The sensors vary their resistance with the temperature. As the temperature rises, the resistance falls. As the temperature falls, the resistance rises. The HVAC control module uses the sensor information to maintain the desired temperature of the passenger cabin air.
Air Distribution Door Actuator
The air distribution door actuator contains a reversible electric motor and a potentiometer. The potentiometer allows the HVAC control module to monitor the position of the airflow mode door.
Air Inlet Door Actuator
The air inlet door actuator contains a reversible electric motor and a potentiometer. The potentiometer allows the HVAC control module to monitor the position of the airflow mode door. The HVAC control module drives the actuator motor in the direction necessary to move the door to the position set by the recirculation button and when the MAX A/C, Defrost or MAX Defrost buttons are selected.
Temperature Door Actuator
The EATC system has one temperature door actuator located on the passenger side of the climate control housing. The temperature door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the HVAC control module to monitor the position of the temperature blend door.
Evaporator Temperature Sensor
The evaporator temperature sensor contains a thermistor. Sensor resistance varies with evaporator temperature. As the temperature rises, the resistance falls. As the temperature falls, the resistance rises. The evaporator temperature sensor is an input to the HVAC control module and the information is relayed to the PCM over the HS-CAN . If the temperature is below approximately 2°C (35.6°F), the PCM does not allow the A/C compressor clutch to engage.
Service Gauge Port Valves
The service gauge port fitting is an integral part of the refrigerant line or component.
Item | Description | Torque |
1 | Low-pressure service gauge port valve cap | 7 lb.in ( .8 Nm) |
2 | Low-pressure service gauge port valve O ring | — |
3 | Low-pressure Schrader-type valve | 16 lb.in ( 1.8 Nm) |
4 | Low-pressure service gauge port valve | — |
5 | High-pressure service gauge port valve | — |
6 | High-pressure Schrader-type valve | 22 lb.in ( 2.5 Nm) |
7 | High-pressure service gauge port valve O ring | — |
8 | High-pressure service gauge port valve cap | 7 lb.in ( .8 Nm) |
Refrigerant System Dye
NOTE: Check for leaks using a Rotunda-approved UV lamp and dye enhancing glasses.
A fluorescent refrigerant system dye wafer is added to the receiver drier desiccant bag at the factory to assist in refrigerant system leak diagnosis. This fluorescent dye wafer dissolves after about 30 minutes of continuous A/C operation. It is not necessary to add additional dye to the refrigerant system before diagnosing leaks, even if a significant amount of refrigerant has been removed from the system. REFER to the appropriate procedure in General Procedures.
Replacement desiccant bags, either separately or part of the receiver drier assembly, are equipped with a new fluorescent dye wafer. It is not necessary to add additional dye to the refrigerant system before diagnosing leaks. If the system has been out of refrigerant through the winter the dye at the leak point may have oxidized and may not fluoresce. If this happens, recharge and operate the A/C system to circulate the oil and allow any residual dye to show up at the leak point. It is important to understand that dye adheres to the oil not the refrigerant; the refrigerant carries the oil out of the leak point.
Electric Booster Heater System
For system operation and component description information on the electric booster heater.
Refer
to: Supplemental Climate Control - System Operation and Component
Description (412-03 Supplemental Climate Control, Description and
Operation).
Cabin Coolant Heater For Supplemental Climate Control
For
system operation and component description information on the cabin
coolant heater for supplemental climate control for hybrid vehicles.
Refer
to: Supplemental Climate Control - System Operation and Component
Description (412-03 Supplemental Climate Control, Description and
Operation).
Locating the Under Hood Fuse Box
Accessing the Under Hood Fuse Box