System Operation
System Diagram
Item | Description |
---|---|
1 | IPC |
2 | GWM |
3 | HVAC control module |
4 | Rear air distribution door actuator |
5 | Rear temperature door actuator |
6 | Rear blower motor relay |
7 | Rear blower motor speed control |
8 | Rear blower motor |
9 | RHVAC control module |
Network Message Charts
Module Network Input Messages - APIM
Broadcast Message | Originating Module | Message Purpose |
---|---|---|
Climate control status | HVAC control module | This message contains the HVAC climate control settings for the touch screen display. |
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:
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:
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 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.
WARNING: Airbags can kill or injure a child in a child restraint. Never place a rear-facing child restraint in front of an active airbag. If you must use a forward-facing child restraint in the front seat, move the seat upon which the child restraint is installed all the way back.