1999 LAND ROVER DISCOVERY Workshop Manual

AIR CONDITIONING
DESCRIPTION AND OPERATION 82-21
DESCRIPTION AND OPERAT ION
Rear A/C refrigerant system component
layout
1Rear evaporator/blower assembly
2Refrigerant lines
3Connections to front A/C system

AIR CONDITIONING
82-22DESCRIPTION AND OPERATION
Rear A/C distribution and control
component layout
1Control panel
2Rear evaporator/blower assembly3Air distribution ducts
4Vent assembly

AIR CONDITIONING
DESCRIPTION AND OPERATION 82-23
Description
The rear air conditioning system cools and recirculates air at the rear of the cabin. The system consists of refrigerant
lines, a rear evaporator/blower assembly, a distribution system and a control panel.
Cooled air from the rear evaporator/blower assembly is supplied by the distribution system to vent outlets above each
second and third row seat. The system is controlled by two switches on the control panel.
Refrigerant lines
Two refrigerant lines connect the rear evaporator/blower assembly to the front A/C refrigerant system. The lines are
routed along the LH underside of the vehicle and secured to a connector block in the floor. A heat shield protects the
lines where they pass above the rear silencer.

AIR CONDITIONING
82-24DESCRIPTION AND OPERATION
Rear evaporator/blower assembly
1Resistor pack
2Thermostatic expansion valve
3Rear blower relay
4Air outlet
5Evaporator6Capillary tube
7Housing
8Condensate drain outlet
9Refrigerant lines
10Blower
The rear evaporator/blower assembly cools and dehumidifies air from the cabin and supplies it to the rear distribution
system. The unit is installed on the left side of the loadspace, behind the quarter trim. A grille in the quarter trim allows
air to flow from the loadspace into the evaporator/blower. Refrigerant lines for the evaporator and a condensate drain
tube are attached to the rear floor.
The evaporator and blower are installed in a common housing, which also incorporates the resistor pack for the
blower. A thermostatic expansion valve is integrated into the inlet refrigerant line. A rear blower relay is attached to
the top of the housing.
Evaporator
The evaporator absorbs heat from the recirculated air being supplied to the distribution ducts.
Thermostatic expansion valve
The thermostatic expansion valve meters the flow of refrigerant into the evaporator to match the heat load of the air
passing through the evaporator matrix. A capillary tube, attached to the outlet pipe of the evaporator and connected
to the thermostatic expansion valve, automatically adjusts the valve opening in relation to the refrigerant temperature
at the evaporator outlet.

AIR CONDITIONING
DESCRIPTION AND OPERATION 82-25
Blower
The blower controls the volume of air being supplied to the distribution outlets. The blower is an open hub, centrifugal
fan powered by an electric motor. A dust filter is installed over the fan inlet. The blower switch on the control panel
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 air outlet
from the blower fan, so that any heat generated is dissipated by the air flow.
Distribution system
Air ducts
Ducts connected to the rear evaporator/blower motor assembly distribute air to five vent assemblies in the roof.
Vent assemblies
The vent assemblies allow occupants to control the flow and direction of air. Each vent assembly incorporates a
thumbwheel to regulate flow and moveable vanes to control direction.
Rear control system
The control system operates the blower to control the operation of the rear A/C. The control system consists of two
control switches and a rear blower relay.
Control switches
A rear A/C switch and a blower speed switch are installed on a control panel in the roof lining. The A/C switch is a
latching pushswitch with an amber indicator lamp which illuminates when rear A/C is selected on. The blower speed
switch is a slide switch with a positive detent at each of four speed positions (there is no off position).
Rear blower relay
The rear blower relay controls the electrical supply to the blower.

AIR CONDITIONING
82-26DESCRIPTION AND OPERATION
Operation
The rear A/C only operates if the front A/C is on to pump refrigerant through the rear evaporator/blower assembly.
When the rear A/C switch is selected on, the indicator lamp in the switch illuminates and the rear blower relay is
energised. The rear blower relay switches battery power to the blower motor, which runs at the speed selected on the
blower speed switch.
The air from the blower passes through the evaporator matrix, which absorbs heat from the air. The cooled air is then
supplied to the roof vents through the distribution ducts. The heat absorbed by the refrigerant in the evaporator is
sensed by the thermostatic expansion valve. The thermostatic expansion valve then opens and regulates the flow of
refrigerant through the evaporator in proportion to the amount of heat being absorbed from the air.
When the rear A/C switch is selected off, the blower stops. The thermostatic expansion valve senses the subsequent
decrease in temperature of the refrigerant in the evaporator. The thermostatic expansion valve then closes and stops
the flow of refrigerant, except for a minimal bleed flow.

AIR CONDITIONING
REFRIGERANT RECOVERY, RECYCLING AND RECHARGING 82-27
REFRIGERANT RECOVERY, RECYCLING AND RECHARGING
Refrigerant recovery, recycling and
recharging
$% 82.30.02
Recovery
1.Remove dust caps from high and low pressure
connectors.
2.Connect high and low pressure hoses to
appropriate connections.
3.Open valves on connectors.
4.Turn valves on refrigerant station to correct
positions.
Operate the refrigerant station in accordance
with the manufacturers instructions.
5.Turn Process switch to correct position.
6.Turn Main switch to 'ON'.
7.Allow station to recover refrigerant from
system.
WARNING: Refrigerant must always be
recycled before re-use to ensure that the
purity of the refrigerant is high enough for
safe use in the air conditioning system.
Recycling should always be carried out with
equipment which is design certified by
Underwriter Laboratory Inc. for compliance
with SAE J1991. Other equipment may not
recycle refrigerant to the required level of
purity.
A R134a Refrigerant Recovery Recycling
Recharging Station must not be used with
any other type of refrigerant.
Refrigerant R134a from domestic and
commercial sources must not be used in
motor vehicle air conditioning systems.
8.Close valves on refrigerant station.
9.Turn Main switch to 'OFF'.
10.Close valves on connectors.
11.Disconnect connectors high and low pressure
hoses from connectors.
12.Fit dust caps to connectors. 13.Open tap at rear of station to drain refrigerant
oil.
14.Measure and record quantity of refrigerant oil
recovered from system.
15.Close tap at rear of station.
Evacuation
WARNING: Servicing must only be carried
out by personnel familiar with both the
vehicle system and the charging and testing
equipment. All operations must be carried
out in a well ventilated area away from open
flame and heat sources.
1.Remove dust caps from high and low pressure
connectors.
2.Connect high and low pressure hoses to
appropriate connections.
3.Open valves on connectors.
4.Turn valves on refrigerant station to correct
positions.
5.Turn Process switch to correct position.
6.Turn Main switch to 'ON'.
7.Allow station to evacuate system.