1995 LAND ROVER DISCOVERY light

AIR CONDITIONING
3
DESCRIPTION AND OPERATION AIR CONDITIONING SYSTEM OPERATION
The air conditioning system provides the means of
supplying cooled and dehumidified, fresh or
recirculated air to the interior of the vehicle. The
cooling effect is obtained by blowing air through the
matrix of an evaporator unit and when required,
mixing that air with heated air by means of the heater
distribution and blend unit, to provide the conditions
required inside the vehicle. The volume of conditioned
air being supplied is controlled by a variable speed
blower.
A sealed system, charged with Refrigerant R134a,
together with a blower unit, blend unit and control
system combine to achieve the cooled air condition.
For air conditioning air distribution system.
See
HEATING AND VENTILATION, Description and
operation, Heating and ventilation unit
The air conditioning system comprises five major
units:
1.An engine-mounted compressor.
2.A condenser mounted in front of the radiator.
3.A receiver/drier unit located in front of the
condenser.
4.Thermostatic expansion valve mounted above
the evaporator.
5.An evaporator unit mounted in front of the heater
matrix.
NOTE: Vehicles fitted with rear air
conditioning have an additional
evaporator/blower motor assembly located
behind the LH rear compartment lower trim panel.
These units are interconnected by hoses and pipes
carrying Refrigerant R134a, the evaporator is linked
into the vehicle ventilation system.
Refrigeration cycle
1. Compressor
The compressor (1), belt driven from the crankshaft
pulley, pressurises and circulates the refrigerant
through the system. Mounted on the compressor, an
electro-mechanical clutch maintains the correct
temperature and pressure by engaging or disengaging
to support the system's requirements. The clutch
action is normally controlled by a thermostat located
at the evaporator (5). The compressor is of the
swashplate type having fixed displacement.Should the temperature at the evaporator (5) fall low
enough for ice to begin to form on the fins, the
thermostat disengages the clutch and also isolates the
cooling fans relays. When the temperature at the
evaporator (5) rises to the control temperature, the
clutch is re-engaged.
Should the system pressure become excessive or
drop sufficiently to cause damage to the compressor
(1) a dual pressure switch (7), located in the high
pressure line, signals the relay unit to disengage the
clutch. The compressor also has an emergency high
pressure relief valve (9) fitted.
The cooling fans are controlled by engine temperature
when the air conditioning is not switched on.
2. Condenser
From the compressor, hot high pressure vaporised
refrigerant (F1) passes to the condenser (2), which is
mounted in front of the engine coolant radiator. Ram
air(A1) passing through the condenser (2),
supplemented by 2 cooling fans (8) mounted in front
of the condenser, cools the refrigerant vapour
sufficiently to form a high pressure slightly subcooled
liquid (F2).
3. Receiver/drier
This liquid then passes to a receiver/drier (3) which
fulfils two functions. It acts as a reservoir and moisture
extractor (11).
A sight glass (10), in the high pressure line, provides a
method of determining the state of the refrigerant
without breaking into the system.
4. Expansion valve
From the receiver/drier (3) the moisture free high
pressure liquid refrigerant (F3) passes through a
thermostatic expansion valve (4). A severe pressure
drop occurs across the valve and as the refrigerant
enters the evaporator space at a temperature of
approximately -5°C it boils and vaporises.

82AIR CONDITIONING
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DESCRIPTION AND OPERATION 5. Evaporator
As this change of state occurs, a large amount of
latent heat is absorbed. The evaporator is therefore
cooled and as a result heat is extracted from the air
flowing across the evaporator. The air flow is
controlled by the ventilation fan which can be
operated at anyone of four speeds.
To prevent liquid passing through to the compressor,
a capillary tube (6), attached to the outlet pipe of the
evaporator (5) and connected to the thermostatic
expansion valve (4), controls the amount that the
valve opens and closes in relation to the temperature
of the low pressure high temperature refrigerant
vapour (F4) at the outlet. The atomised refrigerant
then passes through the evaporator (5). Fan blown air
(A2) passes through the matrix (A3) of the evaporator
and is cooled by absorption due to the low
temperature refrigerant passing through the
evaporator.
A thermostat is fitted in the airflow out of the
evaporator to sense the temperature of the exterior
fins. Should ice begin to form, due to a too cold
condition, it will signal to disengage the
electro-mechanical clutch on the compressor (1).
From the evaporator, low pressure slightly
superheated refrigerant (F5) passes to the
compressor to complete the cycle.AIR CONDITIONING CONTROL SYSTEM
The air conditioning control system comprises relays,
thermostat, pressure switches, and a control panel.
Inputs from outside the air conditioning system
comprise temperature information from the engine
cooling system. Together these controls, in
conjunction with the cooling fans, compressor clutch,
blower and heater distribution and blend unit enable
minimal input to maintain the required environment
inside the vehicle.
When air conditioning is not selected, air is supplied
by ram effect or blower to the areas selected by the
controls. The air mix flap on the blend unit controls the
temperature of the air being supplied. No cooled air is
available.
Selecting air conditioning provides the added facility of
cooled air available to be mixed as before. When
required a fully cold condition can be selected by
turning the temperature controls to cold, which
automatically closes the heated coolant access to the
heater matrix. Mixtures of cooled, fresh, and hot air
can be selected to give required interior environmental
conditions by selection at the control panel.
Dual pressure switch
This switch, located in the high pressure line between
the receiver drier and the expansion valve, monitors
refrigerant pressure and by means of the relay module
controls the following system functions:
1.Refrigerant pressure drops below 2.0 bar, 29
lbf/in
2(due to possible leakage), the
compressor's electro-mechanical clutch is
dis-engaged.
When pressure rises above 2.0 bar, 29 lbf/in
2the
compressor's clutch is re-engaged.
2.Refrigerant pressure rises above 32 bar, 455
lbf/in
2(due to possible blockage), even with
cooling fan operation, the compressor's
electro-mechanical clutch is dis-engaged.
When the pressure drops below 26 bar, 375
lbf/in
2the compressor clutch is re-engaged.

AIR CONDITIONING
1
REPAIR PRECAUTIONS IN HANDLING REFRIGERANT
LINES
WARNING: Wear eye and hand protection
when disconnecting components
containing refrigerant. Plug all exposed
connections immediately.
1.When disconnecting any hose or pipe
connection the system must be discharged of all
pressure. Proceed cautiously, regardless of
gauge readings. Open connections slowly,
keeping hands and face well clear, so that no
injury occurs if there is liquid in the line. If
pressure is noticed, allow it to bleed off slowly.
2.Lines, flexible end connections and components
must be capped immediately they are opened to
prevent the entrance of moisture and dirt.
3.Any dirt or grease on fittings must be wiped off
with a clean alcohol dampened cloth. Do not use
chlorinated solvents such as trichloroethylene. If
dirt, grease or moisture cannot be removed from
inside the hoses, they must be replaced with
new hoses.
4.All replacement components and flexible end
connections must be sealed, and only opened
immediately prior to making the connection.
5.Ensure the components are at room temperature
before uncapping, to prevent condensation of
moisture from the air that enters.
6.Components must not remain uncapped for
longer than fifteen minutes. In the event of delay,
the caps must be fitted.
7.Receiver/driers must never be left uncapped as
they contain Silica Gel crystals which will absorb
moisture from the atmosphere. A receiver/ drier
left uncapped must not be used, fit a new unit.
8.The compressor shaft must not be rotated until
the system is entirely assembled and contains a
charge of refrigerant.
9.A new compressor contains an initial charge of
of refrigerant oil. The compressor also contains a
holding charge of gas when received which
should be retained by leaving the seals in place
until the pipes are re-connected.10.The receiver/drier should be the last component
connected to the system to ensure optimum
dehydration and maximum moisture protection of
the system.
11.All precautions must be taken to prevent
damage to fittings and connections. Slight
damage could cause a leak with the high
pressures used in the system.
12.Always use two wrenches of the correct size,
one on each fitting when releasing and
tightening refrigeration unions.
13.Joints and 'O' rings should be coated with
refrigeration oil to aid correct seating. Fittings
which are not lubricated with refrigerant oil are
almost certain to leak.
14.All lines must be free of kinks. The efficiency of
the system is reduced by a single kink or
restriction.
15.Flexible hoses should not be bent to a radius
less than 90mm.
16.Flexible hoses should not be within 100mm of
the exhaust manifold.
17.Completed assemblies must be checked for
refrigeration lines touching metal panels. Any
direct contact of lines and panels transmits noise
and must be eliminated.

AIR CONDITIONING
11
REPAIR THERMOSTAT
Service repair no - 86.25.50
Remove
1.Remove heater and cooler unit.
See Heater
and Cooler Unit
2.Remove lower cover and evaporator.See
Evaporator and Expansion Valve
3.Remove 5 clips and screw securing evaporator
top cover.
4.Remove evaporator top cover.
5.Remove thermostat sensor from evaporator
matrix.
6.Remove 2 screws securing sensor unit.
7.Remove thermostat and insulation.
Refit
8.Reverse removal procedure.
CAUTION: The thermostat insulation must
be installed in the ORIGINAL POSITION in
the evaporator.EVAPORATOR/BLOWER MOTOR ASSEMBLY -
REAR
Service repair no - 82.26.01
Remove
1.Recover refrigerant from system.
See
Adjustment, refrigerant recovery recycling
recharging
WARNING: Wear eye and hand protection
when disconnecting components
containing refrigerant. Plug all exposed
connections immediately.
2.Remove evaporator to alpine light duct.
See
evaporator to alpine light duct
3.Remove LH rear mud flap.See CHASSIS AND
BODY, Repair, mud flap - rear - lh
4.Clean area around low and high pressure air
conditioning pipe unions, beneath rear wheel
arch, to prevent any risk of dirt entering the
system.
5.Loosen and disconnect high and low pressure
air conditioning pipe unions beneath rear wheel
arch.
6.Remove and discard 'O' rings from pipe unions.
CAUTION: Use 2 spanners when loosening
or tightening air conditioning pipe unions.
CAUTION: Plug exposed connections
immediately.

82AIR CONDITIONING
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REPAIR
7.Remove nut securing rear fold down seat
mounting frame to wheel arch.
8.Remove 5 bolts securing rear fold down seat
mounting frame.
NOTE: The rear fold down seat mounting
frame retaining nut is located in the LH
rear wheel arch.
9.Remove mounting frame.
10.Disconnect 2, main to rear air conditioning unit
harness multiplugs.
11.Remove 3 bolts securing evaporator/blower
motor assembly to body.
12.Release evaporator/blower motor assembly
pipes from body grommets.
13.Remove evaporator/blower motor assembly.Refit
14.Lubricate body grommets to aid fitment of
evaporator/blower motor assembly pipe unions.
15.Fit evaporator/blower motor assembly, feed pipe
unions through grommets and align to fittings.
16.Fit bolts securing evaporator/blower motor
assembly to body and tighten to
25 Nm.
17.Connect, main to rear air conditioning unit,
harness multiplugs.
18.Position and align rear fold down seat mounting
frame to fittings, fit nut and bolts and tighten to
25 Nm.
19.Lubricate NEW 'O' rings with refrigerant oil, and
fit to pipe unions.
20.Remove plugs, align unions, and tighten to;
High pressure pipe:
14 Nm
Low pressure pipe:22 Nm.
CAUTION: Use 2 spanners when loosening
or tightening air conditioning pipe unions.
21.Fit LH rear mud flap.
See CHASSIS AND
BODY, Repair, mud flap - rear - lh; Refit
22.Fit evaporator to alpine light duct.See
evaporator to alpine light duct; Refit
23.Evacuate and recharge air conditioning system.
See Adjustment, refrigerant recovery
recycling recharging

82AIR CONDITIONING
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REPAIR EVAPORATOR - REAR
Service repair no - 82.26.08
Remove
1.Remove evaporator/blower motor assembly
harness.
See harness - evaporator/blower
motor assembly - rear
2.Remove foam seal from evaporator to alpine
light duct flange.
3.Remove screw securing air conditioning
pressure pipe 'P' clip to casing.
4.Remove 4 screws securing evaporator/blower
motor lower casing.
5.Remove lower casing.
6.Remove foam insulation from expansion valve
and expansion valve probe.
7.Loosen expansion valve to evaporator union.
CAUTION: Use 2 spanners when loosening
or tightening air conditioning pipe unions.
8.Remove and discard 'O' ring from evaporator
pipe.
9.Plug expansion valve to evaporator connections.
10.Remove expansion valve probe retaining clip.

AIR CONDITIONING
19
REPAIR
11.Remove 6 screws securing evaporator/blower
motor casing halves.
12.Remove 4 clips securing evaporator/blower
motor casing halves.
13.Separate evaporator/blower motor casing whilst
extracting the thermostat probe from evaporator
matrix.
14.Remove evaporator.Refit
15.Position evaporator and align to casing.
16.Position casing halves together whilst inserting
thermostat probe into evaporator matrix.
NOTE: Ensure thermostat probe is
positioned correctly through casing.
17.Fit clips securing evaporator/blower motor
casing halves.
18.Fit and tighten screws securing
evaporator/blower motor casing halves.
19.Position expansion valve probe to evaporator
pipe and secure with clip.
20.Remove plugs from expansion valve and
evaporator pipe connections.
21.Lubricate NEW 'O' ring and fit to evaporator
pipe.
22.Position expansion valve to evaporator pipe and
tighten union to
22 Nm.
CAUTION: Use 2 spanners when loosening
or tightening air conditioning pipe unions.
23.Remove backing paper from NEW foam
insulation.
24.Fit foam insulation to expansion valve and
expansion valve probe.
25.Position evaporator/blower motor lower casing
and secure with screws.
26.Position air conditioning pressure pipe 'P' clip to
evaporator/ blower motor casing and secure with
screw.
27.Remove backing paper from NEW
foam,evaporator to alpine light duct, flange seal.
28.Fit foam seal to evaporator/blower motor casing
flange.
29.Fit evaporator/blower motor assembly harness.
See harness - evaporator/blower motor
assembly - rear; Refit

82AIR CONDITIONING
20
REPAIR THERMOSTAT - REAR
Service repair no - 82.26.09
Remove
1.Remove evaporator/blower motor assembly
harness.
See harness - evaporator/blower
motor assembly - rear
2.Remove foam seal from evaporator to alpine
light duct flange.
3.Remove screws securing 2 relay mounting
brackets to evaporator/blower motor casing and
position aside.
4.Disconnect 2 Lucars from thermostat.
5.Loosen 2 screws securing thermostat.
6.Release thermostat from bracket.
7.Remove 2 clips securing evaporator/blower
motor casing halves.
8.Remove screw securing evaporator/blower
motor casing halves.
9.Separate casing sufficiently to enable removal of
thermostat probe from casing.
10.Remove thermostat.
Refit
11.Position thermostat fixings to casing and tighten
screws.
12.Connect Lucars to thermostat.
13.Separate casing sufficiently to enable fitment of
thermostat probe to casing.
14.Fit and tighten screw securing casing halves.
15.Fit clips securing casing halves.
16.Remove backing paper from NEW foam,
evaporator to alpine light duct, flange seal.
17.Fit foam seal to evaporator/blower motor casing
flange.
18.Fit evaporator/blower motor assembly harness.
See harness - evaporator/blower motor
assembly - rear; Refit