Lincoln Navigator: Rear Climate Control / Rear Climate Control - System Operation and Component Description. Description and Operation

System Operation

System Diagram

*.sttxt { visibility: hidden; } *.stcallout { visibility: visible; } E370663 1 Center display 2 GWM 3 APIM 4 RACM 5 FCIM 6 Rear air discharge temperature sensor 7 Rear footwell air discharge temperature sensor 8 Rear temperature sensor 9 Rear blower motor relay 10 Rear blower motor 11 Rear blower motor speed control 12 Rear temperature door actuator 13 Rear air distribution door actuator 14 Microphone

Item	Description
1	Center display
2	GWM
3	APIM
4	RACM
5	FCIM
6	Rear air discharge temperature sensor
7	Rear footwell air discharge temperature sensor
8	Rear temperature sensor
9	Rear blower motor relay
10	Rear blower motor
11	Rear blower motor speed control
12	Rear temperature door actuator
13	Rear air distribution door actuator
14	Microphone

Network Message Chart

  Module Network Input Messages APIM

Broadcast Message	Originating Module	Message Purpose
Climate control button status	FCIM control module	This message contains the HVAC climate control settings for the touch screen display

  Module Network Input Messages FCIM 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 touchscreen inputs.
Rear climate control function status	RACM	This message contains the rear climate control function status.
A/C clutch status	PCM	This message contains the status of the A/C compressor clutch.

  Module Network Input Messages RACM

Broadcast Message	Originating Module	Message Purpose
HVAC rear blower indicator status	FCIM control module	This message contains the HVAC rear blower indicator status.
HVAC rear blower status	FCIM control module	This message contains the status of the HVAC rear blower.
A/C clutch status	PCM	This message contains the status of the A/C compressor clutch.

Rear Climate Controls

For diagnosis and testing of the rear climate control system,
Refer to: Climate Control System (412-00 Climate Control System - General Information, Diagnosis and Testing).
.

The rear climate control system operation is determined by the settings on the Touchscreen (if equipped), front climate control panel selection or from the RACM panel selection. The rear climate control components are hard wired to the FCIM control module. Air is cooled and dehumidified by the rear A/C evaporator core only if the front (main) climate control system is operating in a mode that requires A/C compressor operation. The rear system requests are sent to the FCIM control module over the MS-CAN .

Rear Climate Controls - Front DATC

The customer interface from the front (main) DATC panel for the rear climate system consists of the following selections:

• Rear fan speed control: Adjusts the volume of air circulated to the rear passenger compartment.
• Rear passenger power: Press to switch the rear system on and off.
• Rear control lock: When illuminated, you can only operate the rear passenger settings through the front controls.
• Rear air distribution control: Press to switch the direction of airflow.
• Rear passenger temperature control: Adjusts the temperature setting for the rear passenger compartment.
• Rear AUTO: Press to switch on automatic operation.

Rear Climate Controls - Rear Auto

The customer interface from the rear climate control panel consists of the following selections:

• Rear fan speed control: Adjusts the volume of air circulated to the rear passenger compartment.
• Rear passenger power: Press to switch the rear system on and off.
• Rear control lock: When illuminated, you can only operate the rear passenger settings through the front controls.
• Rear air distribution control: Press to switch the direction of airflow.
• Rear passenger temperature control: Adjusts the temperature setting for the rear passenger compartment.
• Rear AUTO: Press to switch on automatic operation.

For illustrations and rear climate control button operation information, refer to the Owner's Literature.

Rear Climate Controls Front Touchscreens

The customer interface from the touchscreen has access to the rear climate control system. The rear climate control system can be accessed in the lower right corner of the main touchscreen under climate.

For more illustrations and rear climate control button operation information, refer to the Owner's Literature.

Control System Logic

When a selection has been made on the rear climate control panel, known as the RACM , a message is sent to the FCIM control module over the MS-CAN .

Air Handling

The rear climate control system has the following features:

• The rear blower motor recirculates the air inside the vehicle. Outside air is not available to the rear system.
• The rear temperature door and the rear air distribution door are controlled by electric actuator motors
• Movement of the rear mode control between PANEL and FLOOR causes a corresponding movement of the rear air distribution door to direct airflow between the overhead registers and the floor duct.
• An air distribution duct supplies conditioned air to the rear passenger compartment to the passengers through adjustable registers.

The FCIM control module sends a PWM signal to the rear blower motor to control the blower speed. The rear blower motor provides variable ground feed for the blower motor

Component Description

Rear Audio Control Module (RACM)

The RACM is located in the second row on the rear of the center floor console. The RACM also depending on the optional trim package and region can be located on the second row arm rest between the second row captain chairs. The RACM contains both rear HVAC controls and audio controls. It is used by the rear vehicle occupants to request changes to the rear climate control system. The requests are sent to the FCIM control module over the MS-CAN then relayed through the GWM by the HS-CAN3 to the RACM .

For more information about the RACM ,
Refer to: Information and Entertainment System - System Operation and Component Description (415-00 Information and Entertainment System - General Information - Vehicles With: SYNC 4, Description and Operation).

Rear Air Discharge Temperature Sensor

The rear air discharge temperature sensor is located in the passenger side upper c-panel trim. The rear air discharge temperature sensor contains a thermistor and is an input to the FCIM control module. The sensor varies its resistance with the temperature. As the temperature rises, the resistance falls. As the temperature falls, the resistance rises. The FCIM control module uses the sensor information to help maintain the desired temperature of the rear passenger cabin air.

Rear Air Distribution Door Actuator

The rear air distribution door actuator moves the rear air distribution door on command from the FCIM control module based on input from either the front or rear climate controls.

The rear air distribution door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the FCIM control module to monitor the position of the rear air distribution door. 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 FCIM control module from the contact wiper indicates the position of the rear air distribution door.

Rear Blower Motor

The rear climate control system contains a blower motor, which is controlled by either the front or rear climate controls. The rear blower motor is mounted to the Rear Climate Control Housing.

Rear Blower Motor Speed Control

The rear blower motor speed control uses a PWM signal from the FCIM control module to determine the desired blower speed and varies the ground feed for the blower motor to control the speed. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.

Rear Footwell Air Discharge Temperature Sensor

The rear footwell air discharge temperature sensor is located in the passenger side lower c-panel trim. The rear footwell air discharge temperature sensor contains a thermistor and is an input to the FCIM control module. The sensor varies its resistance with the temperature. As the temperature rises, the resistance falls. As the temperature falls, the resistance rises. The FCIM control module uses the sensor information to help maintain the desired temperature of the rear passenger cabin air.

Rear Temperature Sensor

The rear temperature sensor, located in the rear of the headliner next to the active noise control microphone, contains a thermistor and is an input to the FCIM control module. The sensor varies its resistance with the temperature. As the temperature rises, the resistance falls. As the temperature falls, the resistance rises. The FCIM control module uses the sensor information to help maintain the desired temperature of the rear passenger cabin air.

Rear Temperature Door Actuator

The rear temperature door actuator moves the rear temperature door on command from the FCIM control module based on input from either the front or rear climate controls.

The rear temperature door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the FCIM control module to monitor the position of the rear temperature door. 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 FCIM control module from the contact wiper indicates the position of the rear temperature door.

Rear Heater Core

The rear heater core consists of fins and tubes arranged to extract heat from the engine coolant and transfer the heat to air passing through the Rear Climate Control Housing.

Rear Evaporator Core

The rear evaporator core is an aluminum tube/fin type heat exchanger located in the rear climate control housing. A mixture of liquid refrigerant and oil enters the rear evaporator through the rear evaporator inlet tube and continues out of the rear evaporator through the rear evaporator outlet tube as a vapor. During A/C compressor operation, airflow from the rear blower motor is cooled and dehumidified as it flows through the rear evaporator fins.

Rear Thermostatic Expansion Valve (TXV)

The Rear Thermostatic Expansion Valve (TXV) restricts the flow of refrigerant from the high-pressure side of the refrigerant system and separates the low-pressure and high-pressure sides of the rear refrigerant system. Refrigerant entering and exiting the rear 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 rear evaporator core and adjusts an internal pin-type valve to meter the refrigerant flow into the rear evaporator core. The internal pin-type valve decreases the amount of refrigerant entering the rear evaporator core at lower temperatures and increases the amount of refrigerant entering the rear evaporator core at higher temperatures.