Lincoln Nautilus: Climate Control System - General Information / Climate Control System - System Operation and Component Description. Description and Operation

System Operation

System Diagram

E385077 *.sttxt { visibility: hidden; } *.stcallout { visibility: visible; } 1 Microphone 2 APIM 3 GWM 4 Ambient Air Temperature (AAT) sensor 5 A/C pressure transducer 6 A/C clutch relay 7 A/C compressor clutch field coil 8 Externally Controlled Variable Displacement Compressor (EVDC) 9 Sunload sensor 10 In-vehicle temperature and humidity sensor 11 Driver side footwell air discharge temperature sensor 12 Passenger side footwell air discharge temperature sensor 13 Driver side register air discharge temperature sensor 14 Passenger side register air discharge temperature sensor 15 Cabin heater coolant pump 16 Blower motor relay 17 Blower motor speed control 18 Blower motor 19 PCM 20 Evaporator temperature sensor 21 Air distribution door actuator 22 HVAC Control Module 23 Air inlet door actuator 24 FDIM 25 FCIMB 26 Ambient air quality sensor (if equipped) 27 Driver temperature door actuator 28 Passenger temperature door actuator

Item	Description
1	Microphone
2	APIM
3	GWM
4	Ambient Air Temperature (AAT) sensor
5	A/C pressure transducer
6	A/C clutch relay
7	A/C compressor clutch field coil
8	Externally Controlled Variable Displacement Compressor (EVDC)
9	Sunload sensor
10	In-vehicle temperature and humidity sensor
11	Driver side footwell air discharge temperature sensor
12	Passenger side footwell air discharge temperature sensor
13	Driver side register air discharge temperature sensor
14	Passenger side register air discharge temperature sensor
15	Cabin heater coolant pump
16	Blower motor relay
17	Blower motor speed control
18	Blower motor
19	PCM
20	Evaporator temperature sensor
21	Air distribution door actuator
22	HVAC Control Module
23	Air inlet door actuator
24	FDIM
25	FCIMB
26	Ambient air quality sensor (if equipped)
27	Driver temperature door actuator
28	Passenger temperature door actuator

Network Message Chart

  Module Network Input Messages APIM

Broadcast Message	Originating Module	Message Purpose
Climate control button status	HVAC Control Module	This message contains the climate control button status.

  Module Network Input Messages HVAC Control Module

Broadcast Message	Originating Module	Message Purpose
Ambient air temperature	PCM	This message contains raw value from the ambient air temperature sensor.
Climate control requests	APIM	This message contains both the climate control system voice commands as well as all climate control system touch screen inputs.
A/C clutch status	PCM	This message contains the status of the A/C compressor clutch.

  Module Network Input Messages PCM

Broadcast Message	Originating Module	Message Purpose
HVAC A/C request	HVAC Control Module	This message requests the A/C compressor to be engaged.
Evaporator temperature	HVAC Control Module	This message contains the evaporator temperature. The PCM uses the evaporator temperature to determine the A/C compressor output.

The Refrigerant Cycle

For information regarding basic HVAC 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 DATC 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 PCM disengages the A/C clutch relay.
• 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.

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

Control System Logic

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

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

When the FDIM touchscreen or voice commands are used and A/C is selected, the APIM sends a request message over the HS-CAN3 to the GWM . The GWM relays the request to the HVAC control module over the MS-CAN . The GWM sends the requests to the PCM over the HS-CAN1 . The PCM controls the A/C clutch relay.

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 sends the request to the PCM over the HS-CAN1 . The PCM controls the A/C clutch relay.

The HVAC control module requires PMI when it is replaced.

A/C Request

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:

• 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 2°C (35.6°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).
• Battery state of charge conditions are within normal parameters.

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. For more information on PCM sensors, refer to the appropriate workshop manual section.

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 will not allow the A/C clutch to engage.

The HVAC control module adjusts the system based on cabin temperature. 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:

• 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.

The heating and ventilation system uses a reheat method to provide conditioned air to the passenger compartment. Temperature blending is controlled by 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 equipped with Auto Start-Stop have a cabin heater coolant pump to help coolant flow to the heater core.

Air Handling

There are 4 door actuators that control the air flow into the passenger compartment:

• Air distribution
• Air inlet
• Driver temperature
• Passenger temperature

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 position of the actuator door. 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, ambient air temperature and sunload.

When an airflow mode, desired driver or passenger temperature, fresh air, or recirculation mode is selected, the HVAC control module will move the actuator motor in the desired direction.

A choice of air distribution door selection through the APIM is selected. This mode door status displays button status on the APIM display. The HVAC Module is responding to the mode change requests of the FCIMB buttons. To review HS-CAN3 network from APIM to FCIMB through GWM to MS-CAN and HVAC Control Module. To see more CAN CAN Network information,
Refer to: Controller Area Network (CAN) Module Communications Network - System Operation and Component Description (418-00A Controller Area Network (CAN) Module Communications Network, Description and Operation).

The HVAC control module sends a PWM signal to the blower motor speed control to regulate the blower speed as necessary. The blower motor speed control 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:

• the HVAC system operates in a manner to achieve and maintain the temperature set by the operator.
• the temperature doors are automatically controlled by the HVAC module based on the temperature setting.
• the A/C compressor is automatically controlled by the PCM from information sent by the HVAC control module, based on the temperature setting. The A/C compressor operates as long as the outside temperature is above approximately 0°C (32°F).
• the blower motor speed is automatically controlled through the blower motor speed control that receives a PWM signal from the HVAC control module based on the temperature setting, but can be manually overridden.
• the HVAC control module controls the air inlet door to recirculate, partially recirculate or open to the fresh air position depending on the in-car temperature and humidity sensor inputs.

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 allowing only recirculated air.
• the recirculated air indicator is illuminated (recirculated air forced on).
• the footwell vent doors and defrost vent/register doors operate in combination to direct airflow to the instrument panel registers.
• the temperature doors move to the full cool position. Air temperature can be manually overridden.
• the A/C button is illuminated.
• the A/C compressor operates as long as 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 footwell vent doors and defrost vent/register doors operate in combination to direct airflow to the instrument panel registers.
• blended air temperature is available. Only when A/C compressor operation has been selected by pressing the A/C button (indicator on) can the airflow temperature be cooled below the outside air temperature.
• 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 air distribution doors operate in combination to 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. Only when A/C compressor operation has been selected by pressing the A/C button (indicator on) can the airflow temperature be cooled below the outside air temperature.
• 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 air distribution doors operate in combination to 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. Only when A/C compressor operation has been selected by pressing the A/C button (indicator on) can the airflow temperature be cooled below the outside air temperature.
• 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 air distribution doors operate in combination to direct airflow to the floor duct, the defroster duct and the side window demisters.
• blended air temperature is available. Only when A/C compressor operation has been selected by pressing the A/C button (indicator on) can the airflow temperature be cooled below the outside air temperature.
• the blower motor is on and the speed is adjustable.

MAX DEFROST

When MAX DEFROST mode is selected:

• the recirculated air request button is disabled. The air inlet door opens, allowing only outside air into the passenger compartment.
• the air distribution doors operate in combination to 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 mode. The A/C compressor operates as long as the outside temperature is above approximately 0°C (32°F).
• the temperature is set to the highest setting and is not adjustable.
• the fan is set to the highest speed and is not adjustable.
• MAX DEFROST can be exited by pressing the AUTO button.

MyTemp

The MyTemp feature can be used to store and recall a preset driver's 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 MyTemp, refer to the Owner's Literature.

Remote Start - Message Center Set To Auto

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. For additional information on the remote start feature and the other vehicle systems, refer to the Owner's Literature.

Set the climate control to operate in Auto mode through the information display controls: Remote Start > Climate Control > Heater–A/C > Auto. The climate control system automatically sets the interior temperature to 72°F (22°C). Refer to the Owner's Literature for more information.

When the factory remote start feature is used, the DATC system automatically sets certain parameters in an attempt to achieve a comfortable cabin temperature. These parameters are set based on multiple inputs including the in-vehicle temperature and humidity, sunload and outside air temperature sensors.

Remote Start - Message Center Set To Last User Settings

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. For additional information on the remote start feature and the other vehicle systems, refer to the Owner's Literature.

Set the climate control to operate using the last climate control settings through the information display controls: 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. The climate control system cannot be adjusted during remote start operation. Turn the ignition on to return the system to its previous settings. Refer to the Owner's Literature for more information.

Component Description

Air Discharge Temperature Sensors

There are 4 air discharge temperature sensors in the Dual Automatic Temperature Control (DATC) system:

• Driver side register air discharge temperature sensor
• Driver side footwell air discharge temperature sensor
• Passenger side register air discharge temperature sensor
• Passenger side footwell air discharge temperature sensor

All 4 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 the in-vehicle temperature and humidity sensor information.

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 temperature is below approximately 1°C (33.8°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 information and entertainment display unit 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).

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.

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 .

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 door(s). After passing through the heater core, the airflow is distributed to the selected outlet by the airflow mode doors.

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. The receiver drier is integral to the A/C condenser.

Driver Temperature Door Actuator

The driver 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.

Evaporator Core

The evaporator core is an aluminum tube and fin design heat exchanger located in the climate control housing. A mixture of liquid refrigerant and oil enters through the evaporator core inlet tube and exits 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.

Evaporator Temperature Sensor

The evaporator temperature sensor contains a thermistor. The 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 1°C (33.8°F), the PCM does not allow the A/C compressor clutch to engage.

Externally Controlled Variable Displacement A/C 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).

The externally controlled variable displacement 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.
• Refer to Specifications in Group 412 for the appropriate refrigerant and refrigerant oil. 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.

Variable displacement compressors have a swash plate that rotates to reciprocate pistons, which compresses refrigerant. Variable displacement compressors change the swash plate angle to change the refrigerant displacement. The externally controlled variable displacement compressor changes the swash plate angle in response to an electrical signal from the PCM . The externally controlled variable displacement compressor manages displacement by controlling refrigerant differential pressure before and after a throttle at the discharge side; achieving precise cooling capability control in response to cabin environment and driving conditions.

The PCM sends a PWM signal to the solenoid in the compressor to control the compressor displacement based upon the:

• Ambient air temperature
• Evaporator temperature
• Engine RPM
• Vehicle speed
• A/C high side pressure
• Temperature and mode settings of the climate control head
• Intake air temperature

Heater Core

The heater core, located in the climate control housing, consists of fins and tubes arranged to extract heat from the engine coolant and transfer it to air passing through the heater core.

HVAC Control Module - Dual Automatic Temperature Control (DATC)

The Dual Automatic Temperature Control (DATC) system uses the HVAC control module, and it also controls the outputs for rear window defrost and climate controlled seats. For vehicles equipped with touchscreen audio, the Dual Automatic Temperature Control (DATC) system uses voice commands or the touchscreen to control the system. For details on the HVAC control module communication, refer to Control System Logic in this section.

The HVAC control module utilizes a Field-Effect Transistor (FET) protective circuit strategy for its actuator outputs. Output load (current level) is monitored for excessive current (typically short circuits) and is shut down (turns off the voltage or ground provided by the module) when a fault event is detected. A short circuit DTC is stored at the fault event and a cumulative counter is started.

When the demand for the output is no longer present, the module resets the Field-Effect Transistor (FET) circuit protection to allow the circuit to function. The next time the driver requests a circuit to activate that has been shut down by a previous short (Field-Effect Transistor (FET) protection) and the circuit is still shorted, the Field-Effect Transistor (FET) protection shuts off the circuit again and the cumulative counter advances.

When the excessive circuit load occurs often enough, the module shuts down the output until a repair procedure is carried out. The Field-Effect Transistor (FET) protected circuit has 3 predefined levels of short circuit tolerance based on the harmful effect of each circuit fault on the Field-Effect Transistor (FET) and the ability of the Field-Effect Transistor (FET) to withstand it. A module lifetime level of fault events is established based upon the durability of the Field-Effect Transistor (FET). If the total tolerance level is determined to be 600 fault events, the 3 predefined levels would be 200, 400 and 600 fault events.

When each tolerance level is reached, the short circuit DTC that was stored on the first failure cannot be cleared by a command to clear the Diagnostic Trouble Codes (DTCs). The module does not allow the DTC to be cleared or the circuit to be restored to normal operation until a successful self-test proves that the fault has been repaired. After the self-test has successfully completed (no on-demand Diagnostic Trouble Codes (DTCs) present), DTC U1000:00 and the associated DTC (the DTC related to the shorted circuit) automatically clears and the circuit function returns.

When each level is reached, the DTC associated with the short circuit sets along with DTC U1000:00. These Diagnostic Trouble Codes (DTCs) can be cleared using the module self-test, then the Clear DTC operation on the scan tool. The module never resets the fault event counter to zero and continues to advance the fault event counter as short circuit fault events occur.

If the number of short circuit fault events reach the third level, then Diagnostic Trouble Codes (DTCs) U1000:00 and U3000:49 set along with the associated short circuit DTC . DTC U3000:49 cannot be cleared and a new module must be installed after the repair.

The FCIM requires PMI when it is replaced.

Particulate Matter Sensor (if equipped)

The particulate matter sensor measures very small particulate matter in the cabin air. It is a hard wired input to the HVAC control module. When calibrated amounts of particles are detected, the air inlet door position automatically changes as needed.

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.

In-Vehicle Temperature And Humidity Sensor

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 does not contain a fan motor. 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.

Passenger Temperature Door Actuator

The passenger 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.

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.

Refrigerant System Dye

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. For more information for leak detection,
Refer to: Fluorescent Dye Leak Detection - Vehicles With: R1234YF Refrigerant (412-00 Climate Control System - General Information) .
or Refer to: Fluorescent Dye Leak Detection - Vehicles With: R1234YF Refrigerant (412-00 Climate Control System - General Information) .

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 dual dye to show up at the leak point. It is important to understand that dye adheres to the oil not the rant; the refrigerant carries the oil out of the leak point.

NOTE: Check for leaks using a Rotunda-approved Ultraviolet (UV) lamp and dye enhancing glasses.

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.

The receiver drier element is incorporated onto the LH side of the A/C condenser.

Service Gauge Port Valves

Item	Description	Torque
1	Low-pressure service gauge port valve cap	0.8 Nm (7 lb-in)
2	Low-pressure service gauge port valve	—
3	Low-pressure Schrader-type valve	1.8 Nm (16 lb-in)
4	High-pressure Schrader-type valve	2.5 Nm (22 lb-in)
5	High-pressure service gauge port valve	—
6	High-pressure service gauge port valve cap	0.8 Nm (7 lb-in)

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

• Prior to leak testing, blow air over the service gauge port valves to ensure 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 General Procedures in Group 412.

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.

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 TXV provides a restriction to the refrigerant flow and separates the low-pressure and high-pressure sides of the refrigerant system. Refrigerant entering and exiting the evaporator core passes through the 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.