Ford Explorer: Rear Climate Control / Description and Operation - Rear Climate Control - System Operation and Component Description

System Operation

System Diagram

Network Message Charts

  Module Network Input Messages - APIM

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 front HVAC control panel selection or from the RHVAC control panel selection. The rear climate control components are hard wired to the HVAC 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.

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 passenger temperature control
• Rear climate control lock
• Rear passenger power
• Rear fan speed control

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

Rear Climate Controls - Front Touchscreen (if equipped)

The customer interface from the touchscreen has access to the rear climate control system. In the lower right of the main touchscreen, touch Climate. On the climate screen, touch Rear from the lower right corner. Rear climate control settings appear at the bottom of the screen:

• Touch the power icon to turn the rear climate control functions off and on.
• Touch Rear Control to allow the rear seat passengers to adjust the rear climate settings. Touch it again to prevent the rear seat passengers from adjusting the settings. Rear Control automatically turns off when you use the touchscreen to adjust the rear climate settings.
• Touch + or – to adjust the temperature.
• To adjust fan speed, touch + or – next to the fan icon.
• Touch Rear again to close the rear controls. Closing the rear climate control functions does not affect their current settings.

For 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 RHVAC control module, a message is sent to the HVAC control module over the MS-CAN.

Air Handling

The rear climate control system has the following features:

• The driver has primary control of the rear climate control system or can transfer control to the rear passenger control panel.
• 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 temperature control between cool and warm causes a corresponding movement of the rear temperature door to mix air flowing through and around the rear heater core.
• 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 panel (headliner) registers and the floor duct.
• A vertical air distribution duct supplies air to the integral headliner air distribution duct. Airflow is then directed to the passengers through adjustable registers. The heater floor duct supplies air to a fixed register, which is integral to the side trim panel.

The HVAC control module sends a PWM signal to the rear blower motor speed control to control the blower speed. The rear 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.

Component Description

Rear Air Distribution Door Actuator

The rear air distribution door actuator moves the rear air distribution door on command from the HVAC 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 HVAC 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 HVAC control module from the contact wiper indicates the position of the rear air distribution door.

Rear Temperature Door Actuator

The rear temperature door actuator moves the rear temperature door on command from the HVAC 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 HVAC 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 HVAC control module from the contact wiper indicates the position of the rear temperature door.

Rear Blower Motor

The rear blower motor is a variable speed motor that pulls air from the vehicle interior and forces it through the rear climate control housing and the rear climate control air distribution ducts.

Rear Blower Motor Speed Control

The blower motor speed control is a solid-state switch that uses a PWM signal from the HVAC control module to determine the desired rear blower motor 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 Climate Control Housing

The rear climate control housing directs airflow from the rear blower motor through the rear evaporator core and rear heater core. All airflow from the rear blower motor passes through the rear evaporator core. The airflow is then distributed to the selected outlet by the airflow mode doors.

Rear Evaporator

The rear evaporator core is an aluminum plate-and-fin type heat exchanger and is located in the rear climate control housing. A mixture of liquid refrigerant and oil enters the rear evaporator core through the rear evaporator core inlet tube and continues out of the rear evaporator core through the rear evaporator core 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 core fins.

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 Heating, Ventilation and Air Conditioning (RHVAC) Control Module

The RHVAC control module is used by the rear vehicle occupants to request changes to the rear climate control system. The requests are sent to the HVAC control module over the MS-CAN.

Rear Thermostatic Expansion Valve (TXV)

The rear Thermostatic Expansion Valve (TXV) is located at the rear evaporator core inlet and outlet tubes. The rear Thermostatic Expansion Valve (TXV) provides a restriction to the flow of refrigerant 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 rear Thermostatic Expansion Valve (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.

Rear A/C - Heater Inlet and Outlet Lines

The rear climate control system A/C and heater inlet and outlet lines are part of a bundle of 4 aluminum tube assemblies of various sizes bracketed together and fastened to the underbody of the vehicle.