Description

Heating and Ventilation

NOTE:
A = Hardwired; N = Medium speed CAN (controller area network) bus; O = LIN (local interconnect network) bus; P = Media orientated system transport (MOST) ring.









Operation of the heating and ventilation system is controlled by the ATC (automatic temperature control) module. For additional information, refer to Control Components Description
The system can be operated in automatic or manual mode, with temperature settings selected using the switches on the integrated control panel.
When the engine is running, coolant is constantly circulated through the heater core by the engine coolant pump and the auxiliary coolant pump. Where fitted, the auxiliary coolant pump is energized by the CJB (central junction box) on receipt of medium speed CAN (controller area network) bus signals from the ATC (automatic temperature control) module. The CJB (central junction box) broadcasts auxiliary coolant pump status over the medium speed CAN (controller area network) bus for use by other vehicle systems.
The blower is supplied with power by the blower relay on the RJB (rear junction box) and connected to ground via the blower control module. The blower control module regulates the voltage across the blower motor to control blower speed. The voltage set by the blower control module is controlled by a PWM (pulse width modulation) signal from the ATC (automatic temperature control) module. The ATC (automatic temperature control) module uses a feedback signal from the blower control module to monitor blower speed. For additional information, refer to Control Components Description

Heater Assembly
The heater assembly controls the temperature and flow of air supplied to the air distribution ducts. The heater assembly is mounted on the vehicle centerline, between the instrument panel and the engine bulkhead.
The heater assembly consists of a casing that contains an A/C (air conditioning) evaporator, a heater core, two air distribution control doors and two temperature blend control doors. On 2.7L diesel vehicles, the heater assembly also contains an electric booster heater. For additional information, refer to Electric Booster Heater Description
Mounted on the heater casing are four stepper motors. Each of the stepper motors is connected to either an air distribution control door or a temperature blend control door.
The A/C (air conditioning) evaporator is part of the A/C (air conditioning) system. For additional information, refer to Air Conditioning Description
The heater core provides the heat source to warm the air supplied to the passenger compartment. The heater core is an aluminum two pass, fin and tube heat exchanger, and is installed across the width of the heater housing. Two aluminum tubes attached to the heater core extend through the engine bulkhead and connect to the engine cooling system. For additional information, refer to Engine Cooling
For additional information, refer to Engine Cooling
For additional information, refer to Engine Cooling Description

Air Inlet Duct
The air inlet duct connects the fresh air inlet in the engine bulkhead to the heater assembly. The air inlet duct is installed behind the instrument panel on the passenger side.
The air inlet duct consists of a casing that contains a pollen filter, an air inlet door, a blower and a blower control module. A recirculation air inlet is incorporated into the casing. A servo motor is mounted on the casing and connected to the air inlet door, to allow selection between fresh and recirculated air. For additional information, refer to Control Components Description
The pollen filter is part of the air distribution and filtering system. For additional information, refer to Air Distribution and Filtering Description
The blower regulates the volume of air flowing through the air inlet duct to the heater assembly. The blower consists of an open hub, centrifugal fan and an electric motor.
The blower control module regulates the power supply to the blower motor. The blower control module is installed in the air inlet duct downstream of the blower, where any heat generated during operation is dissipated by the air flow.

Auxiliary Coolant Pump
On all vehicles except 3.0L, an auxiliary coolant pump is installed on the rear right side of the radiator housing, in the return line from the heater core. The auxiliary coolant pump is an electric pump that boosts the flow of coolant through the heater core.

Ventilation Outlets
The ventilation outlets allow the free flow of air through the passenger compartment. The outlets are installed in the LH and RH rear quarter panels, below the rear lamps. Each ventilation outlet consists of a grille covered by a soft rubber flap, and is effectively a non-return valve. The flaps open and close automatically depending on the pressure differential between the air inside and outside the vehicle.