412-00 Climate Control System - General Information	2014 Fiesta
Description and Operation	Procedure revision date: 05/16/2013

Climate Control System - Vehicles With: Electronic Automatic Temperature Control (EATC) - System Operation and Component Description

System Diagram

System Diagram


Item	Description
1	Evaporator temperature sensor
2	Ambient air temperature (AAT) sensor
3	IPC
4	PCM
5	A/C pressure transducer
6	A/C compressor clutch
7	Center register air discharge temperature sensor
8	Footwell air discharge temperature sensor
9	Sunload sensor
10	In-vehicle temperature sensor
11	HVAC control module
12	Blower motor speed control
13	Blower motor
14	Air distribution door actuator motor
15	Air distribution door actuator position sensor
16	Temperature door actuator motor
17	Temperature door actuator position sensor
18	Air inlet door actuator motor

System Operation

Network Message Chart

Module Network Input Messages — Powertrain Control Module (PCM)

Broadcast Message	Originating Module	Message Purpose
Air Conditioning (A/C) request	HVAC control module	This message requests the A/C compressor to be engaged.
Ambient air temperature	IPC	This message contains raw value from the Ambient Air Temperature (AAT) sensor.
Evaporator temperature	IPC	This message contains the evaporator temperature. The PCM uses the evaporator temperature to cycle the A/C compressor clutch.

Module Network Input Messages — Heating, Ventilation, and Air Conditioning (HVAC) Control Module

Broadcast Message	Originating Module	Message Purpose
Ambient air temperature	IPC	This message contains raw value from the Ambient Air Temperature (AAT) sensor.
Evaporator temperature	IPC	This message contains the evaporator temperature information.

The Refrigerant Cycle

During A/C system shutdown, the refrigerant pressures are equal throughout the system. When the A/C compressor is in operation, it increases pressure on the refrigerant vapor, raising its temperature. The high-pressure and high-temperature vapor is then released into the top of the A/C condenser core.

The A/C condenser, being close to ambient temperature, causes the refrigerant vapor to condense into a liquid when heat is removed from the refrigerant by ambient air passing over the fins and tubing. The now liquid refrigerant, still at high pressure, exits from the bottom of the A/C condenser and enters the inlet side of the A/C receiver/drier. The receiver/drier is designed to remove moisture from the refrigerant.

The outlet of the receiver/drier is connected to the Thermostatic Expansion Valve (TXV). The Thermostatic Expansion Valve (TXV) provides the orifice, which is the restriction in the refrigerant system which separates the high and low pressure sides of the A/C system. As the liquid refrigerant passes across this restriction, its pressure and boiling point are reduced.

The liquid refrigerant is now at its lowest pressure and temperature. As it passes through the A/C evaporator, it absorbs heat from the airflow passing over the tube and fin sections of the A/C evaporator. This addition of heat causes the refrigerant to boil (convert to gas). The now cooler air can no longer support the same humidity level of the warmer air and this excess moisture condenses on the exterior of the evaporator tubes and fins and drains outside the vehicle.

The refrigerant cycle is repeated with the A/C compressor, increasing the pressure and temperature of the refrigerant.

The PCM controls the A/C clutch relay. The evaporator temperature sensor monitors the evaporator core discharge air temperature 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 vehicle PCM .

The line pressure is monitored so A/C compressor operation capacity may vary and may be 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-Gasoline Turbocharged Direct Injection (GTDI)

Thermostatic Expansion Valve (TXV) Type Refrigerant System-Twin Independent Variable Cam Timing (TiVCT)

Control System Logic

Controls and Compressor Operation

All customer climate control requests for the EATC system are inputted through the HVAC control module.

Heating and Ventilation

The heating and ventilation system:

controls the temperature of the air inside the vehicle.
reduces the relative humidity of the air inside the vehicle (during A/C compressor operation).
delivers heated or cooled air to maintain the vehicle interior temperature and comfort level.

Electric Booster Heater

For information on the electric booster heater operation and diagnostics, refer to Section 412-02.

A/C (Air Conditioning) Request

When the A/C is requested, the HVAC control module sends the message over the MS-CAN to the IPC . The IPC sends the A/C request to the PCM through the HS-CAN .

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 0.6ºC (33ºF).
a Wide Open Throttle (WOT) condition is not present.
the evaporator discharge air temperature is above approximately 1.5ºC (35ºF).

Compressor Clutch

When A/C is requested and all conditions are within normal parameters, 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.

Sensor Inputs

The Ambient Air Temperature (AAT) sensor and the evaporator temperature sensor are inputs to the IPC and the information is relayed to the PCM over the HS-CAN . If the temperature is below a predetermined value, the PCM does not allow the A/C clutch to engage.

The sunload sensor is an input to the HVAC control module indicating the intensity of the sun on the vehicle and the HVAC control module compensates high sun load with higher blower and reduced discharge temperatures.

The in-vehicle temperature sensor is an input to the HVAC control module. The HVAC control module adjusts the system based on the temperature of the passenger compartment air.

The center register air discharge temperature sensor and the footwell air discharge temperature sensor are inputs to the HVAC control module and the HVAC control module adjusts the system based on the outlet air temperature.

Air Handling

All airflow from the blower motor passes through the evaporator core. Based on the climate control panel settings, the temperature door actuator directs airflow through the heater core as needed. The air distribution door actuator controls the airflow to the defrost, footwell or register vents. The air source is from outside air or recirculated passenger compartment air as determined by the air inlet door position.

The air distribution door and temperature door actuators use a potentiometer to sense and communicate the door positions to the HVAC control module. When an airflow mode, desired temperature or fresh air or recirculation mode is selected the HVAC control module drives the actuator motor in the direction necessary to make the actuator position agree with the expected HVAC control module position to be obtained.

The HVAC control module sends a PWM signal to the blower motor speed control to control the blower speed. The blower motor speed control 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 actuator is automatically controlled by the HVAC control module based on the temperature setting.
the mode door actuator is automatically controlled by the HVAC control module based on the temperature setting.
the temperature 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 will not operate if the outside temperature is below approximately 0.6ºC (33ºF).
the blower motor is on. The blower motor speed is automatically controlled by the HVAC control module based on the temperature setting, but can be manually overridden.

OFF

When OFF is selected:

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 is selected:

the air inlet door closes, preventing outside air and admits 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 door moves 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 0.6ºC (33ºF).
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.
the recirculated air request button can be enabled.
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 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

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 A/C request button toggles the indicator on and off. To reduce fogging, the A/C compressor operates automatically, regardless of indicator status, if the outside temperature is above approximately 0.6ºC (33ºF).
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 on in defrost. The A/C compressor operates as long as the outside temperature is above approximately 0.6ºC (33ºF).
blended air temperature is available.
the blower motor is on and the speed is adjustable.

Component Description

Component Description

Heating Ventilation Air Conditioning (HVAC) Control Module - Electronic Automatic Temperature Control (EATC)

All customer requests for the EATC climate control system come through the HVAC control module. The HVAC control module adjusts the climate control system components to achieve the desired state based on the temperature selection and sensor inputs.

Blower Motor

The blower motor pulls air from the air inlet and forces it into the heater core and evaporator core housing and the plenum chamber where it is mixed and distributed.

Blower Motor Speed Control

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 heater core and evaporator core housing. A mixture of liquid refrigerant and oil enters the bottom of 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.

Heater Core and Evaporator Core Housing

The heater core and evaporator core 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 door. After passing through the heater core, the airflow is distributed to the selected outlet by the airflow mode doors.

Air Distribution Door Actuator

The air distribution door actuator contains a reversible electric motor and 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 airflow mode doors to the position set by the mode selector knob.

Air Inlet Door Actuator

The air inlet door actuator moves the air inlet door between the fresh and recirculated air positions on command from the HVAC control module. The air inlet mode door actuator is driven to, and automatically stops at, the full recirculated air or full fresh air inlet position and does not require a potentiometer circuit to monitor its position. The airflow mode door does not stop at any point between the recirculated air or fresh air inlet position.

Temperature Door Actuator

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 door. The HVAC control module drives the temperature door actuator motor in the direction necessary to move the temperature door to the position set by the temperature selection knob.

Ambient Air Temperature Sensor

The Ambient Air Temperature (AAT) sensor is an input to the IPC . The Ambient Air Temperature (AAT) sensor contains a thermistor. The sensor varies its resistance with the temperature. As the temperature rises, the resistance falls. As the temperature falls, the resistance rises.

Evaporator Temperature Sensor

The evaporator temperature sensor is an input to the IPC . The evaporator temperature sensor contains a thermistor. The sensor varies its resistance with the temperature. As the temperature rises, the resistance falls. As the temperature falls, the resistance rises.

In-Vehicle Temperature Sensor

The in-vehicle temperature sensor contains a thermistor which measures the in-vehicle air temperature and sends that reading to the HVAC control module. The in-vehicle temperature sensor has an electric fan within the sensor that draws in-vehicle air across the thermistor.

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 and reduced discharge temperatures.

Air Conditioning (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.

Air Conditioning (A/C) Compressor Clutch

When battery voltage is applied to the A/C compressor clutch field coil, the clutch plate and hub assembly is drawn toward the A/C clutch pulley. The magnetic force locks the clutch plate 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 plate and hub assembly move the clutch plate 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 Variable Displacement Air Conditioning (A/C) Compressor

NOTE: Variable compressors operate at lower pressures and are dependent on correct system charge for normal operation.

The internal variable displacement A/C compressor has:

a non-serviceable shaft seal.
a non-serviceable pressure relief valve installed in the rear of the compressor to protect the refrigerant system against excessively high refrigerant pressures.
Motorcraft® Polyalkylene Glycol (PAG) Refrigerant Compressor Oil YN-12-D. This oil contains special additives required for the A/C compressor. The oil may have some slightly dark-colored streaks while maintaining normal oil viscosity. This is normal for this A/C compressor because of break-in wear that can discolor the oil.

Internal variable displacement A/C compressors are internally similar to fixed displacement compressors with a number of pistons placed around an angled plate that are pushed back and forth as the plate rotates. Internal variable displacement compressors vary the angle of the plate to allow piston displacement to be varied from 5% (default) to 100% of full capacity to meet cooling demand.

The displacement is controlled with an internal bellows actuated control valve which senses the intake low side (suction) pressure of the A/C refrigerant gas. The pressure varies with the temperature in the vehicle's cabin. The valve regulates the amount of refrigerant being discharged to maintain an optimum compressor displacement.

Air Conditioning (A/C) Condenser

The A/C condenser is an aluminum tube and fin design heat exchanger. It cools compressed refrigerant gas by allowing air to pass over tubes and fins 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.

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.

Service Gauge Port Valves

The service gauge port fitting is an integral part of the refrigerant line or component.

Prior to leak testing, blow air over service gauge port valves to insure an accurate test.
Special couplings are required for both the high-side and low-side service gauge ports.
A very small amount of leakage around the Schrader-type valve with the service gauge port valve cap removed is considered normal. Install a new Schrader-type valve core if the seal leaks excessively.
The A/C service gauge port valve caps are used as primary seals in the refrigerant system to prevent leakage through the Schrader-type valves from reaching the atmosphere. Always install and tighten the A/C service gauge port valve caps to the correct torque after they are removed.
Follow the procedure and the notes for electronic leak testing.
Refer to: Electronic Leak Detection (412-00 Climate Control System - General Information, General Procedures).

Item	Torque	Description
1	0.8 Nm (7 lb-in)	Low-pressure service gauge port valve cap
2	—	Low-pressure service gauge port valve
3	2.26 Nm (20 lb-in)	Low-pressure Schrader-type valve
4	3.4 Nm (30 lb-in)	High-pressure Schrader-type valve
5	—	High-pressure service gauge port valve
6	0.8 Nm (7 lb-in)	High-pressure service gauge port valve cap

Refrigerant System Dye

A fluorescent refrigerant system dye wafer is added to the receiver/drier desiccant bag to assist in refrigerant system leak diagnosis using a Rotunda-approved UV blacklight. 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.