Description

Description

General
The heating and ventilation system controls the temperature and distribution of air supplied to the vehicle interior. Air is drawn into a heater assembly through a connector hose and an air inlet duct or, on vehicles with air conditioning, the cooling unit.

In the heater assembly, the air can be heated and supplied as required to fascia and floor level outlets. An electrical variable speed blower, and/or ram effect when the vehicle is in forward motion, forces the air through the system. Temperature, distribution and blower controls are installed on a panel on the centre console.

Up to 2002 MY, diesel models in colder climate markets incorporate a Fuel Burning Heater (FBH) in the engine coolant supply to the heater assembly. From 2002 MY, only diesel models in the coldest of those markets retain the FBH; diesel models in the remainder of those markets incorporate an electric Positive Temperature Coefficient (PTC) heater, inside the heater assembly, instead of the FBH.

Air Inlet Duct







The air inlet duct connects the passenger's side of the plenum to the heater assembly, to provide the fresh air inlet. The upper end of the duct locates in a slot in the body and the lower end of the duct is connected to the heater assembly via a corrugated connector hose. A pollen filter is installed in the air inlet duct and retained by two scrivets.

Heater Assembly







The heater assembly heats and distributes air as directed by selections made on the control panel. The assembly is installed on the vehicle centre-line, between the fascia and the engine bulkhead.

The heater assembly consists of a two-piece plastic casing containing a blower, resistor pack, heater matrix and control flaps. The casing on some diesel models also contains a PTC heater. Integral passages guide the air through the casing from the inlet to the distribution outlets. A wiring harness connects the blower and resistor pack to the blower switch on the control panel.

Blower
The blower controls the volume of air being supplied to the distribution outlets. The blower is installed in the driver's side of the casing and consists of an open hub, centrifugal fan powered by an electric motor. The open end of the fan surrounds the air inlet, which is on the passenger's side of the casing. The blower switch and the resistor pack control the operation of the blower, which can be selected to run at one of four speeds.

Resistor Pack
The resistor pack supplies reduced voltages to the blower motor for blower speeds 1, 2 and 3. For blower speed 4, the resistor pack is bypassed and battery voltage drives the motor at full speed. The pack is installed in the RH side of the casing, in the air outlet from the blower fan, so that any heat generated is dissipated by the air flow.

Heater Matrix
The heater matrix provides the heat source to warm the air being supplied to the distribution outlets. It is installed in the LH side of the casing behind a protective cover. The matrix is a copper and brass, two pass, fin and tube heat exchanger. Engine coolant is supplied to the matrix through two brass tubes that extend through the bulkhead into the engine compartment. When the engine is running, coolant is constantly circulated through the heater matrix by the engine coolant pump. On diesel some models, the coolant flow is assisted by an electric pump when the FBH system is operating.

Control Flaps
Four control flaps are installed in the heater assembly to control the temperature and distribution of air. A blend flap controls the temperature by directing air inlet flow through or away from the heater matrix. Two distribution flaps control the air flow distribution to the selected vents, and an extra flap closes the air path from the off side of the heater matrix to the blend chamber to reduce heat pick-up causing a rise in temperature at the foot and defrost outlets in comparison to the temperature at the face vent outlets.

Blend Flap: The blend flap regulates the flow of air through the heater matrix to control the temperature of the air leaving the heater assembly. It consists of a hinged flap between the cold air bypass and the heater matrix. The flap hinge is connected to a lever mechanism on the LH side of the casing. A control cable is installed between the lever mechanism and the temperature knob on the control panel to operate the flap. Turning the temperature knob turns the flap and varies the proportions of air going through the cold air bypass and the heater matrix. The proportions vary, between full bypass no heat and no bypass full heat, to correspond with the selection on the temperature knob. When the flow is split between the cold air bypass and the heater matrix, the two flows are mixed downstream of the heater matrix to produce an even air temperature at the individual outlets.

A flap on the air outflow side of the heater matrix is used to close off the path of cold air flowing around the bypass route from picking up heat from the matrix in the blend chamber and so prevent an increase in air temperature when the airflow is diverted to the foot or defrost outlets. The flap hinge is connected to a lever mechanism on the LH side of the casing. A control cable is installed between the lever mechanism and the temperature knob on the control panel to operate the flap. Turning the temperature knob turns the flap. When unheated air is required and the temperature control is at its minimum setting, the 'close-off' flap is completely shut to prevent thermal pick-up. As the temperature control knob is turned up to select a higher ambient temperature, the 'close-off' flap is opened to allow the passage of air flow through the heater matrix to the blend chamber.

Distribution Flaps: A main flap and a fresh air flap control the flow of air to the distribution outlets in the casing. The main flap is a rotating segment that controls the flow to the windscreen/side window and footwell outlets. The fresh air flap is a hinged door that controls the flow to the face level outlets. The hinge of each flap is connected to a common lever mechanism on the RH side of the casing. A control cable is installed between the mechanism and the distribution knob on the control panel to operate the flaps together. Turning the distribution knob turns the flaps to direct air through the corresponding outlets in the casing.













Distribution
Air from the heater assembly is distributed around the vehicle interior through fascia and floor level outlets. Fascia outlets consist of fixed vents for the windscreen and side windows, and adjustable vent assemblies for face level air. Floor level outlets consist of fixed vents for the front and rear footwells.

The front footwell vents are integrated into the heater assembly. Two central vent assemblies for face level air are connected directly onto the related outlets of the heater assembly. Air for the rear footwell, outer face level vent assemblies and windscreen/side windows is distributed through ducts.







Ducts
The rear footwell ducts extend along each side of the transmission tunnel and vent into the rear footwells from below the front seats. The outer face level ducts attach to the underside of the fascia and connect to the vent assembly at each end of the fascia. The windscreen/side window ducts connect to a duct integrated into the top of the fascia.

Vent Assemblies
The vent assemblies allow occupants to control the flow and direction of face level air. Each vent assembly incorporates a thumbwheel to regulate flow and moveable vanes to control direction.

Heating and Ventilation Controls







Rotary knobs are installed on the centre console to control air distribution, blower speed and air temperature. The air distribution and temperature knobs operate cables connected to the control flaps in the heater assembly. The blower speed knob operates a rotary switch in the blower's electrical circuit. Graphics on the control panel indicate the function and operating positions of the controls.







Fuel Burning Heater (FBH) System (Where Fitted)
The FBH system is an auxiliary heating system that compensates for the relatively low coolant temperatures inherent in the diesel engine. At low ambient temperatures, the FBH system heats the coolant supply to the heater assembly, and maintains it within the temperature range required for good in-car heating performance. Operation is fully automatic, with no intervention required by the driver.

The system consists of an ambient air temperature sensor, a FBH fuel pump and a FBH unit. Fuel for the FBH system is taken from the vehicle fuel tank, through a line attached to the fuel tank's fuel pump, and supplied via the FBH fuel pump to the FBH unit. The connection on the fuel tank's fuel pump incorporates a tube which extends down into the tank. In the FBH unit, the fuel delivered by the FBH fuel pump is burned and the resultant heat output is used to heat the coolant. An ECU integrated into the FBH unit controls the operation of the system at one of two heat output levels, 5 kW at full load (i.e. maximum output) and 2.5 kW at part load.

Ambient Air Temperature Sensor







The ambient air temperature sensor controls a power supply, from the alternator via the Engine Control Module (ECM) to the FBH unit. The sensor is installed on a bracket attached to the body behind the RH side of the front bumper valance. The sensor contains a switch that is closed at temperatures below 5 degrees C (41 degrees F) and open at temperatures of 5 degrees C (41 degrees F) and above.

FBH Fuel Pump

On vehicles up to 2002.5 model year - The FBH fuel pump is installed in a rubber mounting in a bracket attached inside the rear RH wheelarch.

On vehicles from 2002.5 model year - The FBH fuel pump is located in a plastic housing which is attached to the filter and pump module assembly in the RH rear wheel arch. The housing slides into slots between the filter and pump and is locked in position by a plastic tab.

The FBH fuel pump regulates the fuel supply to the FBH unit. The pump is a self priming, solenoid operated plunger pump, with a fixed displacement of 0.063 cm3/Hz (0.002 US fl.oz/Hz). The ECU in the FBH unit outputs a pulse width modulated signal to control the operation of the pump. When the pump is de-energised, it provides a positive shut-off of the fuel supply to the FBH unit.

FBH Fuel Pump Nominal Operating Speeds Outputs










The solenoid coil of the FBH fuel pump is installed around a housing which contains a plunger and piston. The piston locates in a bush, and a spring is installed on the piston between the bush and the plunger. A filter insert and a fuel line connector are installed in the inlet end of the housing. A non return valve and a fuel line connector are installed in the fuel outlet end of the housing.

While the solenoid coil is de-energised, the spring holds the piston and plunger in the 'closed' position at the inlet end of the housing. An 'O' ring seal on the plunger provides a fuel tight seal between the plunger and the filter insert, preventing any flow through the pump.

When the solenoid coil is energised, the piston and plunger move towards the outlet end of the housing, until the plunger contacts the bush; fuel is then drawn in through the inlet connection and filter. The initial movement of the piston also closes transverse drillings in the bush and isolates the pumping chamber at the outlet end of the housing. Subsequent movement of the piston then forces fuel from the pumping chamber through the non return valve and into the line to the FBH unit.

When the solenoid de-energises, the spring moves the piston and plunger back towards the closed position. As the piston and plunger move towards the closed position, fuel flows past the plunger and through the annular gaps and transverse holes in the bush to replenish the pumping chamber.

FBH Unit







The FBH unit is installed behind the front bumper, in front of the LH wheelarch. It is connected in series with the coolant supply to the heater assembly. Two electrical connectors on the FBH unit connect it to the vehicle wiring. Spring clamps secure the fuel supply line to a spigot on the FBH unit.







The FBH unit consists of:
- A circulation pump
- A combustion air fan
- A burner housing
- An ECU/heat exchanger
- An air inlet hose
- An exhaust pipe
- An air inlet filter

Circulation Pump
The circulation pump is installed at the coolant inlet to the FBH unit to assist the coolant flow through the FBH unit and the heater assembly. The pump runs continuously while the FBH unit is in standby or active operating modes. While the FBH unit is inactive, coolant flow is reliant on the engine coolant pump.

Combustion Air Fan
The combustion air fan regulates the flow of air into the unit to support combustion of the fuel supplied by the FBH pump and to purge and cool the FBH unit. A canister type filter is included in the air inlet supply line to prevent particulates entering and contaminating the FBH unit.

Burner Housing
The burner housing contains the burner insert and also incorporates connections for the exhaust pipe, the coolant inlet from the circulation pump and the coolant outlet to the heater assembly. The exhaust pipe directs exhaust combustion gases to atmosphere through a pipe below the FBH unit.

The burner insert incorporates the fuel combustion chamber, an evaporator and a glow plug/flame sensor. Fuel from the FBH fuel pump is supplied to the evaporator, where it evaporates and enters the combustion chamber to mix with air from the combustion air fan. The glow plug/flame sensor provides the ignition source of the fuel:air mixture and, once combustion is established, monitors the flame.

ECU Heat Exchanger
The ECU controls and monitors operation of the FBH system. Ventilation of the ECU is provided by an internal flow of air from the combustion air fan. The heat exchanger transfers heat generated by combustion to the coolant. A sensor in the heat exchanger provides the ECU with an input of heat exchanger casing temperature, which the ECU relates to coolant temperature and uses to control system operation. The temperature settings in the ECU are calibrated to compensate for the difference between coolant temperature and the heat exchanger casing temperature detected by the sensor. Typically, as the coolant temperature increases, the coolant will be approximately 7 degrees C (12.6 degrees F) hotter than the temperature detected by the sensor; as the coolant temperature decreases, the coolant will be approximately 2 degrees C (3.6 degrees F) cooler than the temperature detected by the sensor.

PTC Heater System (Where Fitted)
The PTC heater system, like the FBH, is an auxiliary heating system that compensates for the relatively low coolant temperatures inherent in the diesel engine. When the heater blower is selected on (any speed) and the temperature control is selected to the 1 o'clock position or above, i.e. warm to hot, the PTC heater automatically comes on to boost the temperature of the air flowing through the heater assembly. The system consists of:
- The PTC heater.
- A heater switch.
- Two relays.
- A link harness and fuses.

PTC Heater
The PTC heater is installed in the heater assembly on the downstream side of the coolant heater matrix. The PTC heater is an electrical heating element consisting of alternating layers of radiator fins and thermistor elements installed in a frame and secured with spring clips. Plastic end covers on the frame each incorporate two lugs for locating the PTC heater in the heater assembly casing. Silicone caps are installed on the lugs to prevent rattling. Three power supply leads and a common earth lead are connected to the thermistor element layers. A grommet protects the leads where they pass through the heater assembly casing.

The thermistor elements are made of a ceramic based compound which is treated with a semiconductor material to make it conductive. At low temperatures the thermistor elements offer low electrical resistance, but once a predetermined temperature is exceeded their resistance rapidly increases with increasing temperature. This characteristic provides a fast warm-up (less than 10 seconds) of the thermistor elements when they are supplied with electrical power, followed by a temperature regulating effect where the current consumption is matched to the heat output.

When the PTC heater is supplied with electrical power, the thermistor elements heat up to the predetermined temperature. The radiator fins absorb heat from the thermistor elements and transfer it to the air stream.

The PTC heater is rated at 900 W at a nominal operating voltage of 13.5 V, ambient air temperature of 0 degrees C (32 degrees F) and air flow of 5 kg/minute (11 lb/minute). The initial current draw is in the region of 55 to 75 A, depending on the ambient air temperature and the temperature of the PTC heater. The theoretical surface temperature of the PTC heater, without any airflow, is 165 degrees C (329 degrees F) maximum.







Heater Switch
The heater switch controls when the PTC operates. The switch is installed on the rear of the heater control panel and is operated by the spindle of the temperature control knob.

When the temperature control knob is selected in the cold to warm range, i.e. less than approximately 1 o'clock, the heater switch is open and the PTC heater is off. When the temperature control knob is selected in the warm to hot range, i.e. approximately 1 o'clock and above, the heater switch is closed and the PTC heater is on.

Relays
A power relay and a control relay control the switching of power to the PTC heater. The power relay is installed on the engine bulkhead behind the engine compartment fuse box and is operated by the control relay. The control relay is operated by the heater switch. Up to 2004 model year the control relay is installed at the side of the Ebox. From 2004 model year the control relay is installed in the passenger compartment fusebox.

Link Harness and Fuses
The link harness interconnects the PTC heater system components and connects the system to the main harness. The harness is routed from the RH side of the heater assembly, through the engine bulkhead into the plenum, then along the plenum and into the rear right corner of the engine compartment. Grommets protect the link harness where it passes through the engine bulkhead and the front wall of the plenum.

An 80 A in-line fuse is incorporated into the link harness to protect the power feed from the battery to the power relay. Three 30 A fuses, in a fuse holder at the side of the E-box, protect the individual power feeds from the power relay to the PTC heater.