2002 LAND ROVER DISCOVERY heater

HEATING AND VENTILATION
80-6DESCRIPTION AND OPERATION
Control flaps
Control flaps are installed in the heater assembly to control the temperature and distribution of air. Blend flaps control
the temperature and distribution flaps control the distribution.
Temperature and distribution control
Figure shows flaps set for medium heat to face level and footwell outlets
1Windscreen/Side windows outlet
2Heater assembly casing
3Air inlet
4Heater matrix5Front footwells outlet
6Rear footwells outlet
7Face level outlet
Blend flaps:Two sets of three blend flaps, one LH and one RH, regulate the flow of air through the heater matrix and
a heater matrix bypass, to control the temperature of the air leaving the heater assembly. The two sets of blend flaps
operate independently to allow different temperatures to be set for the LH and RH outlets.
Each blend flap is attached to a spindle. The end of each spindle extends through the side of the heater casing and
is attached to a common lever mechanism on the related side of the casing. A control cable is installed between the
lever mechanism and the related temperature knob on the control panel. When the flow is split between the bypass
and the heater matrix, the two flows mix downstream of the heater matrix to produce an even air temperature at the
individual outlets.
Distribution flaps: Separate distribution flaps are installed to control the flow of air to the footwells, windscreen/side
windows and the LH and RH face level outlets. The distribution flaps are attached to spindles that extend through the
RH side of the heater casing and are attached to a common lever mechanism. A control cable is installed between
the lever mechanism and the distribution knob on the control panel.

HEATING AND VENTILATION
DESCRIPTION AND OPERATION 80-7
Distribution ducts
Separate distribution ducts are installed for the front and rear footwell outlets. Distribution ducts for the face level,
windscreen and side windows outlets are integrated into the fascia. The front footwell ducts are attached to ports at
the sides of the heater assembly. The rear footwell ducts locate in ports at the rear of the heater assembly and extend
along each side of the centre console to vent into the rear footwells from below the cubby box.
Vent assemblies in the fascia 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
80-8DESCRIPTION AND OPERATION
Control panel
The controls for heating and ventilation are installed on a control panel in the centre of the fascia, below the radio.
Three rotary knobs control the LH and RH outlet temperatures and distribution. A slider switch controls blower speed.
A latching pushswitch controls the selection of fresh/recirculated air; an amber LED in the switch illuminates when
recirculated air is selected.
Graphics on the panel and the controls indicate the function and operating positions of the controls.
Outlet vent
The outlet vent promotes the free flow of heating and ventilation air through the cabin. The outlet vent is installed in
the RH rear quarter body panel and vents cabin air into the sheltered area between the rear quarter body panel and
the outer body side panel. The vent consists of a grille covered by soft rubber flaps and is effectively a non-return
valve. The flap opens and closes automatically depending on the differential between cabin and outside air pressures.
FBH system (diesel models only)
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 air temperature sensor, a FBH fuel pump and a FBH unit. Fuel for the FBH system is taken
from the 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. At the FBH
unit connection, the fuel line incorporates a self-sealing, quick disconnect coupling. 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, 2.5 kW at part load and 5 kW at full load
Ambient temperature sensor
The ambient temperature sensor controls a power supply from the alternator to the FBH unit. The sensor is installed
on the RH support strut of the bonnet closing panel and contains a temperature sensitive switch that is closed at
temperatures below 5
°C (41 °F) and open at temperatures of 5 °C (41 °F) and above.

HEATING AND VENTILATION
80-10DESCRIPTION AND OPERATION
FBH unit
1Air inlet hose
2Electrical connectors
3Exhaust pipe
4Quick disconnect coupling5Coolant inlet hose
6Fuel supply line
7Circulation pump
8Coolant outlet hose
The FBH unit is installed on the bulkhead in the engine compartment, on the side opposite the brake servo, and is
connected in series in the coolant supply to the heater assembly. Two electrical connectors on the top of the FBH unit
connect to the vehicle wiring.
FBH unit connector pin details
Connector/Pin
No.Description Input/Output
C0925
2 K line (diagnostics) Input/Output
3 Alternator power supply Input
6 FBH fuel pump Output
C0926
1 Battery power supply Input
2Earth -

HEATING AND VENTILATION
80-12DESCRIPTION AND OPERATION
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. It also supplies the air required to purge and cool the FBH unit. Ambient air is supplied to
the combustion air fan through an air inlet hose containing a sound deadening foam ring.
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 at the bottom of the engine compartment.
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
°C (12.6 °F) hotter than the temperature detected by the sensor; as the coolant temperature
decreases, the coolant will be approximately 2
°C (3.6 °F) cooler than the temperature detected by the sensor.

HEATING AND VENTILATION
DESCRIPTION AND OPERATION 80-13
Operation
Air distribution
Turning the distribution knob on the control panel turns the control flaps in the heater assembly to direct air to the
corresponding fascia and footwell outlets.
Air temperature
Turning the LH or RH temperature knob on the control panel turns the related blend flaps in the heater assembly. The
blend flaps vary the proportion of air going through the cold air bypass and the heater matrix. The proportion varies,
between full bypass no heat and no bypass full heat, to correspond with the position of the temperature knob.
Blower speed
The blower can be selected off or to run at one of four speeds. While the ignition is on, when the blower switch is set
to positions 1, 2, 3, or 4, ignition power energises the blower relay, which supplies battery power to the blower. At
switch positions 1, 2 and 3, the blower switch also connects the blower to different earth paths through the resistor
pack, to produce corresponding differences of blower operating voltage and speed. At position 4, the blower switch
connects an earth direct to the blower, bypassing the resistor pack, and full battery voltage drives the blower at
maximum speed.
Fresh/Recirculated inlet air
When the recirculated air switch is latched in, the amber indicator LED in the switch illuminates and an earth is
connected to the recirculated air side of the fresh/recirculated air servo motor. The fresh/recirculated air servo motor
then turns the control flaps in the air inlet duct to close the fresh air inlet and open the recirculated air inlets.
When the latch of the recirculated air switch is released, the amber indicator LED in the switch extinguishes and the
earth is switched from the recirculated air side to the fresh air side of the fresh/recirculated air servo motor. The fresh/
recirculated air servo motor then turns the control flaps in the air inlet duct to open the fresh air inlet and close the
recirculated air inlets.
FBH system (where fitted)
The FBH system operates only while the engine is running and the ambient temperature is less than 5
°C (41 °F).
With the engine running and the ambient temperature below 5
°C (41 °F), the air temperature sensor connects the
alternator power supply to the ECU in the FBH unit. On receipt of the alternator power supply, the ECU starts the
circulation pump and, depending on the input from the temperature sensor in the heat exchanger, enters either a
standby or active mode of operation. If the heat exchanger casing temperature is 65
°C (149 °F) or above, the ECU
enters a standby mode of operation. If the heat exchanger casing temperature is below 65
°C (149 °F), the ECU enters
an active mode of operation. In the standby mode, the ECU monitors the heat exchanger casing temperature and
enters the active mode if it drops below 65
°C (149 °F). In the active mode, the ECU initiates a start sequence and
then operates the system at full or part load combustion to provide the required heat input to the coolant.
Start sequence
At the beginning of the start sequence the ECU energises the glow plug function of the glow plug/flame sensor, to
preheat the combustion chamber, and starts the combustion air fan at slow speed. After 30 seconds, the ECU
energises the FBH fuel pump at the starting sequence speed. The fuel delivered by the FBH fuel pump evaporates in
the combustion chamber, mixes with air from the combustion air fan and is ignited by the glow plug/flame sensor. The
ECU then progressively increases the speed of the FBH fuel pump and the combustion air fan to either part or full
load speed, as required by the system. Once full or part load speed is achieved, the ECU switches the glow plug/flame
sensor from the glow plug function to the flame sensing function to monitor combustion. From the beginning of the
start sequence to stable combustion takes approximately 90 seconds for a start to part load combustion and 150
seconds for a start to full load combustion.

HEATING AND VENTILATION
REPAIRS 80-15
REPAIRS
Heater control and fan switch
$% 80.10.02
Remove
1.Remove louvre panel assembly.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Louvre panel assembly - centre
fascia.
2.Release temperature and air distribution cable
abutments from heater control housing and
disconnect inner cables from controls.
3.Disconnect multiplugs from switches.
4.Disconnect multiplug from control illumination.
5.Remove heater control.
6.Remove 3 switches from heater control.
Refit
1.Fit switches to heater control housing.
2.Position heater control assembly and connect
multiplugs to switches and illumination.
3.Connect heater control cables and secure
outer cable abutments to casing.
4.Fit louvre panel assembly.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Louvre panel assembly - centre
fascia.
Cables - heater control
$% 80.10.06
Remove
1. Driver temperature control and air flow
control cables:Release fixings and lower
fascia fuse box access cover.
2. Passenger temperature control cable:
Remove 4 screws securing glove box, release
catch and remove glove box.

HEATING AND VENTILATION
80-16REPAIRS
3.Remove louvre panel assembly.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Louvre panel assembly - centre
fascia.
4.Release control cable abutment from control
housing and disconnect inner cable from
control.
5.Release clip securing control outer cable to
heater case and disconnect inner cable from
flap lever.
6.Remove control cable. Refit
1.Fit new control cable, connect inner cable to
control and secure abutment to control
housing.
2.Fit other end of inner cable to flap lever.
3.Position control to maximum heat for
temperature control cables or demist for air
flow control cable, hold flap lever in fully closed
position and secure outer cable in clip on
heater casing.
4.Refit louvre panel assembly.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Louvre panel assembly - centre
fascia.
5. Driver temperature and air flow control
cables: Close fuse access cover and secure
fixings.
6. Passenger temperature control cable: Refit
glove box and secure with bolts.