1995 LAND ROVER DISCOVERY oil pressure

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.

AIR CONDITIONING
1
FAULT DIAGNOSIS AIR CONDITIONING FAULTS
FAULT CAUSE REMEDY
1. Incorrect voltage. 1. Check voltage.
A.2. Open or defective fuse or relay. 2. Check and replace as necessary.
BLOWER3. Loose wire connection including 3. Check system wires; tighten
MOTORground. all connections.
INOPERATIVE4. Switch open or defective. 4. Replace switch.
OR SLOW5. Tight, worn, or burnt motor 5. Replace motor.
RUNNINGbearings.
6. Open rotor windings. 6. Replace motor.
7. Worn motor brushes. 7. Replace motor.
8. Shaft binding-blade misaligned. 8. Check alignment. Repair or replace
as necessary.
9. Defective resistors 9. Rectify or replace.
1. Incorrect voltage. 1. Check voltage.
2. Open or defective fuse or relay. 2. Check and replace as necessary.
B.3. Defective thermostat control or 3. Replace thermostat or
COMPRESSORpressure switch. pressure switch.
CLUTCH4. Shorted or open field coil. 4. Replace coil.
INOPERATIVE5. Bearing seized (clutch will not 5. Replace clutch pulley assembly.
disengage).
6. Refrigeration circuit problem causing
heavy load and excessive drive
torque.6. Check and rectify.
1. Incorrect alignment. 1. Check alignment; repair as
necessary.
2. Loose belt. 2. Adjust to proper tension.
C.3. Compressor not mounted securely. 3. Repair as necessary.
COMPRESSOR4. Bearing in clutch-pulley 4. Remove clutch and replace
CLUTCHassembly not pressed in. clutch pulley assembly.
NOISY5. Low voltage to clutch. 5. Check connections and voltage.
6. Clutch will not spin freely. 6. Refer to B5 above.
7. Oil on clutch face. 7. Check compressor seals for leaks.
8. Slipping clutch. 8. Refer to C5 above. Then check air
gap.
9. Overloaded or locked compressor. 9. Repair or replace compressor.
10. Icing. 10. Check for suction line frosting.
Replace expansion valve if
necessary.
Replace receiver/drier if necessary.
D.1. Motor and/or blades improperly 1. Check mountings, adjust as
CONDENSERmounted. necessary.
VIBRATION2. Foreign matter build-up on 2. Clean blades with a suitable
blades. non-inflammable cleaner.
3. Excessive wear of motor bearings. 3. Replace motor.

82AIR CONDITIONING
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FAULT DIAGNOSISFAULT CAUSE REMEDY
E.
NOISY
EXPANSION
VALVE
(steady hissing)1. Low refrigerant charge; evident by
bubbles in sight glass.1. Leak test. Repair or replace
components as required.
F.1. Expansion valve not operating 1. Refer to C-2, C-3, D-1
INSUFFICIENTproperly. and E.
COOLING2. Low refrigerant charge-evident 2. Refer to B-1 and E.
by bubbles in sight glass.
3. Compressor not pumping. 3. Refer to B-2 and B-3
G.1. Belt tension. 1. Adjust belt tension.
COMPRESSOR2. Excessive head pressure. 2. Refer to A-1 through
BELTA-4 and C-6.
SLIPPING3. Incorrect alignment of pulleys 3. Repair as needed.
or worn belt not riding properly.
4. Nicked or broken pulley. 4. Replace as needed.
5. Seized compressor. 5. Replace compressor.
1. Loose or missing mounting bolts. 1. Repair as necessary.
2. Broken mounting bracket. 2. Replace bracket.
3. Loose flywheel or clutch 3. Repair as necessary.
retaining bolt.
H.4. Rough idler pulley bearing. 4. Replace bearing.
ENGINE5. Bent, loose, or improperly 5. Repair as necessary.
NOISEmounted engine drive pulley.
AND/OR6. Defective compressor bearing. 6. Replace bearing.
VIBRATION7. Insecure mountings of 7. Repair as necessary.
accessories; generator, power
steering, air filter, etc.
8. Excessive head pressure. 8. Refer to A-1, A-2, A-3
A-4 and C-6.
9. Incorrect compressor oil level. 9. Refer to compressor Oil
Level Check.
HEATER AND AIR CONDITIONING - CIRCUIT
DIAGRAMS
1.For details of heating and air conditioning
electrics
See Electrical Trouble Shooting
Manual.

82AIR CONDITIONING
2
ADJUSTMENT SERVICING PRECAUTIONS
Care must be taken when handling refrigeration
system components. Units must not be lifted by their
hoses, pipes or capillary lines. Hoses and lines must
not be subjected to any twist or stress. Ensure that
hoses are positioned in their correct run before fully
tightening the couplings, and ensure that all clips and
supports are used. Torque wrenches of the correct
type must be used when tightening refrigerant
connections to the stated value. An additional wrench
must be used to hold the union to prevent twisting of
the pipe.
Before connecting any hose or pipe ensure that
refrigerant oil is applied to the seat of the new '0' ring
but not to the threads.
Check the oil trap for the amount of oil lost.
All protective plugs on components must be left in
place until immediately prior to connection.
The receiver/drier contains desiccant which absorbs
moisture. It must be positively sealed at all times.
CAUTION: Whenever the refrigerant
system is opened, the receiver/drier must
be renewed immediately before evacuating
and recharging the system.
Use alcohol and a clean cloth to clean dirty
connections.
Ensure that all new parts fitted are marked for use
withR134a.
Refrigerant oil
Use the approved refrigerant lubricating oil:
Nippon Denso ND-OIL 8
Unipart R134a ND-OIL8
CAUTION: Do not use any other type of
refrigerant oil.
Refrigerant oil easily absorbs water and must not be
stored for long periods. Do not pour unused oil back
into the container.
When renewing system components, add the
following quantities of refrigerant oil:
Condenser 40ml..........................................................
Evaporator 80ml..........................................................
Pipe or hose 20ml........................................................
Receiver/drier 20ml......................................................
Total of refrigerant oil in system = 180ml = 6.3 Fl
ozA new compressor is sealed and pressurised with
Nitrogen gas, slowly release the sealing cap, gas
pressure should be heard to release as the seal is
broken.
NOTE: A new compressor should always
have its sealing caps in place and must
not be removed until immediately prior to
fitting
Fitting a new compressor
A new compressor is supplied with an oil fill (X) of:
180ml
A calculated quantity of oil must be drained from a
new compressor before fitting.
To calculate the quantity of oil to be drained:
1.Remove sealing plugs from the OLD compressor
2.Invert compressor and gravity drain oil into
measuring cylinder. Rotating the compressor
clutch plate will assist complete draining.
3.Note the quantity of oil drained (Y).
4.Calculate the quantity (Q) of oil to be drained
from the NEW compressor using the following
formula:
X - (Y + 20ml) = Q
Rapid refrigerant discharge
When the air conditioning system is involved in
accident damage and the circuit is punctured, the
refrigerant is discharged rapidly. The rapid discharged
of refrigerant will also result in the loss of most of the
oil from the system. The compressor must be
removed and all the remaining oil in the compressor
drained and refilled as follows:
1.Gravity drain all the oil, assist by rotating the
clutch plate (not the pulley).
2.Refill the compressor with the following amount
of new refrigerant oil:
130ml
3.Plug the inlet and outlet ports.

AIR CONDITIONING
3
ADJUSTMENT SERVICING EQUIPMENT
The following equipment is required for full servicing
of the air conditioning system.
Recovery, recycling and charging station
Leak detector
Thermometer +20°C to -60°C
Safety goggles and gloves
REFRIGERANT RECOVERY RECYCLING
RECHARGING
WARNING: The air conditioning system is
charged with a high pressure, potentially
toxic refrigerant. Repairs or servicing must
only be carried out by an operator 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.
Always wear safety goggles and gloves when
opening refrigerant connections.
WARNING: Wear eye and hand safety
protection. Open connections slowly in
case liquid or pressure is present. Allow to
bleed off slowly.
CAUTION: Overcharging air conditioning
system will cause excessive head
pressure.
An air conditioning portable Refrigerant Recovery
Recycling Recharging Station for use with R134a
refrigerant incorporates all the features necessary to
recover refrigerant R134a from the air conditioning
system, to filter and remove moisture, to evacuate and
recharge with the reclaimed refrigerant. The unit can
also be used for performance testing and air
conditioning system analysis.
The operator must adhere to the equipment
manufacturer's instructions.Recovery and recycling
1. High pressure servicing connection
2. Low pressure servicing connection
1.Connect a Refrigerant Station to the high and
low pressure servicing connections.
2.Operate the refrigerant recovery system
according to the manufacturer's instructions.
3.Measure the amount of oil discharged from the
system. Add an equal amount of new refrigerant
oil to compressor before evacuation sequence.
WARNING: Refrigerant must always be
recycled before reuse, 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.

82AIR CONDITIONING
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ADJUSTMENT Evacuation and recharging
1.Add refrigerant oil to compressor if necessary.
2.Renew the receiver/drier.
CAUTION: When a major repair has been
carried out, a leak test should be carried
out using inert gas.
3.Connect a Refrigerant Station to the high and
low pressure servicing connections.
CAUTION: Whenever the refrigerant
system is opened, the receiver/drier must
be renewed immediately before evacuating
and recharging the system.
4.Operate the refrigerant evacuation system
according to the manufacturer's instructions.
NOTE: If the vacuum reading is below
700mmHg after 15 minutes, suspect a leak
in the system. Partially recharge the
system and check for leaks using an electronic
leak tester. Check suction lines first, then run the
compressor for 5 minutes and then check the high
pressure lines.
CAUTION: The system must be evacuated
immediately before recharging
commences. Delay between evacuation
and recharging is not permitted.
5.Operate the refrigerant recharging system
according to the manufacturer's instructions:-
Refrigerant required to charge system:
Without rear air conditioning = 0.90kg (32 fl/oz)
With rear air conditioning = 1.15kg (40 fl/oz)
6.If the full charge has not been accepted by the
system, start the engine and run it at 1500
rev/min for a minimum of 2 minutes.
Switch on the air conditioning system, open the
car windows, set the temperature control to cold
and switch the blower to maximum speed.
7.Consult Refrigerant Station Manual for correct
procedure to complete the charge.
8.Carry out the air conditioning system
performance test.LEAK TEST SYSTEM
The following instructions refer to an electronic type
Refrigerant Leak Detector for use with R134a, which
are the safest and most sensitive.
CAUTION: When a major repair has been
carried out, a leak test should be carried
out using an inert gas (see below).
1.Place the vehicle in a well ventilated area but
free from draughts, as leakage from the system
could be dissipated without detection.
2.Follow the instructions issued by the
manufacturer of the particular leak detector
being used.
3.Commence searching for leaks by passing the
detector probe around all joints and components,
refrigerant gas is heavier than air.
4.Insert the probe into an air outlet of the
evaporator or into the evaporator drain tube.
Switch the air conditioning blower on and off at
intervals of ten seconds. Any leaking refrigerant
will be gathered in by the blower and detected.
5.Insert the probe between the magnetic clutch
and compressor to check the shaft seal for
leaks.
6.Check all service valve connections, valve plate,
head and base plate joints and back seal plate.
7.Check the condenser for leaks at the pipe
unions.
8.If any leaks are found, the system must be
discharged before rectification.
9.Rectify any leaks and recheck for leaks during
evacuation prior to charging.
Leak test using inert gas
Use Nitrogen or Helium gas.
1.Connect gas line to recharging station.
2.Pressurise system to 3 bar.
3.Carry out leak test as above.

82AIR CONDITIONING
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ADJUSTMENT SYSTEM TEST
1.Place the vehicle in a ventilated, shaded area
free from excessive draught, with the doors and
windows open.
2.Check that the surface of the condenser is not
restricted with dirt, leaves, flies, etc. Do not
neglect to check the surface between the
condenser and the radiator. Clean as necessary.
3.Switch on the ignition and the air conditioner air
flow control. Check that the blower is operating
efficiently at low, medium and high speeds.
Switch off the blower and the ignition.
4.Check that the evaporator condensate drain
tubes are open and clear.
5.Check the tension of the compressor driving belt,
and adjust if necessary.
6.Inspect all connections for the presence of
refrigerant oil. If oil is evident, check for leaks,
and repair as necessary.
NOTE: The compressor oil is soluble in
Refrigerant R134a and is deposited when
the refrigerant evaporates from a leak.
7.Start the engine.
8.Set the temperature controls to cold and switch
the air conditioner blower control on and off
several times, checking that the magnetic clutch
on the compressor engages and releases each
time.9.With the temperature control at maximum
cooling and the blower control at high speed,
warm up the engine and fast idle at 1000
rev/min. Check the sight glass for bubbles or
foam. The sight glass should be generally clear
after five minutes running, occasional bubbles
being acceptable. Continuous bubbles may
appear in a serviceable system on a cool day, or
if there is insufficient air flow over the condenser
at a high ambient temperature.
10.Repeat at 1800 rev/min.
11.Gradually increase the engine speed to the high
range, and check the sight glass at intervals.
12.Check for frosting on the service valves.
13.Check the high pressure hoses and connections
by hand for varying temperature. Low
temperature indicates a restriction or blockage at
that point.
14.Switch off the air conditioning blower and stop
the engine.
15.If the air conditioning equipment is still not
satisfactory, carry out a pressure test as
previously described in this section.
COMPRESSOR DRIVE BELT
Service repair no - 82.10.01.
Tdi -
See ENGINE, Repair, Compressor drive belt
V8i and MpiSee ENGINE, Repair, Drive belt

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.