1995 LAND ROVER DISCOVERY check engine

82AIR CONDITIONING
4
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
4
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.

AIR CONDITIONING
5
ADJUSTMENT AIR CONDITIONING SYSTEM - PERFORMANCE
TEST
WARNING: R134a is hazardous, refer to
the GENERAL PRECAUTIONS given at the
beginning of this section.
Carry out this test with bonnet and doors or windows
open, air conditioning switched on, temperature
control set to cold and blower at maximum speed. Set
the air supply control to supply fresh air.
1.Close low pressure valve on refrigerant station.
2.Close high pressure valve on refrigerant station.
3.Connect a Refrigerant Station to the high and
low pressure servicing connections.4.Insert dry bulb thermometer into cold air outlet
and position dry and wet bulb thermometer close
to outside air inlet.
Do not spill water from the wet thermometer
(psychrometer).
5.Start engine and run it at 1500 rev/min for 10
minutes with air conditioning switched on.
6.Check that sight glass is free of bubbles.
7.Read both pressure gauges and thermometers.
Check readings against table below with
humidity between 60% and 80%. If readings are
incorrect.
See Fault diagnosis, Refrigeration
System Faults.
8.Switch off air conditioning, stop engine,
disconnect test equipment.
Performance range
Intake temperature Outlet temperature Low pressure High pressure
20 - 24°C4-10°C 18 - 28 lbf/in
2213 - 299 lbf/in2
1.2 - 1.9 bar 14.7 - 20.6 bar
25 - 29°C9-19°C 27 - 37 lbf/in2256 - 341 lbf/in2
1.9 - 2.6 bar 17.6 - 23.5 bar
30 - 35°C20-27°C 33 - 47 lbf/in2299 - 384 lbf/in2
2.3 - 3.2 bar 20.6 - 26.5 bar
Table 1
Ambient Compound Gauge High Pressure
Temperature Readings Gauge Readings
ÊC°F bar lbf/in
2bar lbf/in2
16 60 1,03-1,4 15-20 6,9-10,3 100-150
26,7 80 1,4-1,72 20-25 9,6-13,1 140-190
38 100 1,72-2,1 25-30 12,4-15,5 180-225
43,5 110 2,1-2,4 30-35 14,8-17,2 215-250

82AIR CONDITIONING
6
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
5
REPAIR COMPRESSOR
Service repair no - 82.10.20
Remove
1.Disconnect battery negative lead.
2.Recover refrigerant from air conditioning system.
See Adjustment, Refrigerant Recovery
Recycling Recharging
3.Remove screws retaining centre panel to fan
cowl
4.Remove centre panel.
V8i engine illustrated
5.Remove 2 bolts securing hose flanges to
compressor.
WARNING: Wear eye and hand protection
when disconnecting components
containing refrigerant. Plug all exposed
connections immediately.6.Disconnect high pressure hose from
compressor.
7.Disconnect low pressure hose from compressor.
8.Remove 'O' ring from each flange.
9.Disconnect electrical lead from compressor
clutch.
10.Release drive belt from compressor pulley.
See
ENGINE, Repair, Drive Belt
11.Remove 4 bolts securing compressor to
mounting bracket.
12.Remove compressor from mounting bracket.
Refit
13.New compressor to be fitted: Drain oil from new
compressor outlet port. Drain and measure oil
from old compressor. Measure new oil equal to
amount drained from old compressor, add 30 ml
extra to this amount and refill new compressor
through outlet port.
14.Locate compressor in mounting bracket, fit bolts.
Tighten to
25 Nm.
15.Connect electrical lead to compressor clutch.
16.Fit new 'O' rings to high and low pressure hose
flanges, lubricate with refrigerant oil.
17.Engage hose flanges, fit bolts. Tighten to
10
Nm.
18.Fit compressor drive belt.See ENGINE, Repair,
Drive Belt
19.Fit centre panel to fan cowl.
20.Evacuate and recharge air conditioning system.
See Adjustment, Refrigerant Recovery
Recycling Recharging
21.Perform a leak test on disturbed joints.
22.Carry out a functional check.

ELECTRICAL
1
DESCRIPTION AND OPERATION ELECTRICAL EQUIPMENT
DESCRIPTION
The electrical system is Negative ground, and it is
most important to ensure correct polarity of the
electrical connections at all times. Any incorrect
connections made when reconnecting cables may
cause irreparable damage to the semi-conductor
devices used in the generator and regulator. Incorrect
polarity would also seriously damage any
transistorized equipment such as radio and
tachometer etc.
WARNING: During battery removal or
before carrying out any repairs or
maintenance to electrical components
always disconnect the battery negative lead first.
If the positive lead is disconnected with the
negative lead in place, accidental contact of the
wrench to any grounded metal part could cause a
severe spark, possibly resulting in personal
injury. Upon installation of the battery the positive
lead should be connected first.
GENERATOR
The generator is a three phase, field sensed unit. The
rotor and stator windings produce three phase
alternating current, AC, which is rectified to direct
current, DC. The electronic voltage regulator unit
controls the generator output voltage by high
frequency switching of the rotor field circuit. Use only
the correct Vehicle replacement fan belt. Occasionally
check that the engine and generator pulleys are
accurately aligned.
It is essential that good electrical connections are
maintained at all times. Of particular importance are
those in the charging circuit (including those at the
battery) which should be occasionally inspected to
see that they are clean and tight. In this way any
significant increase in circuit resistance can be
prevented.Do not disconnect battery cables while the engine is
running or damage to the semi-conductor devices
may occur. It is also inadvisable to break or make any
connections in the generator charging and control
circuits while the engine is running.
The electronic voltage regulator employs micro-circuit
techniques resulting in improved performance under
difficult service conditions. The whole assembly is
encapsulated in silicone rubber and housed in an
aluminium heat sink, ensuring complete protection
against the adverse effects of temperature, dust, and
moisture etc.
The regulating voltage is set during manufacture to
give the required regulating voltage range of 14.2±
0.2 volts, and no adjustment is necessary. The only
maintenance needed is the occasional check on
terminal connections and wiping with a clean dry
cloth.
The generator system provides for direct connection
of a charge (ignition) indicator warning light, and
eliminates the need for a field switching relay or
warning light control unit. As the warning lamp is
connected in the charging circuit, lamp failure will
cause loss of charge. Lamp should be checked
regularly and spare carried.
When using rapid charge equipment to re-charge the
battery, the battery must be disconnected from the
vehicle.
NOTE: For description and operation of
electrical circuits see separate publication:
Electrical Troubleshooting Manual.

86ELECTRICAL
4
DESCRIPTION AND OPERATION BUILT IN TEST PROCEDURE
The built in test procedure is accessed as follows:
1.Starting conditions: ignition off, doors unlocked,
bonnet [hood] switch depressed.
2.Carry out instructions 3 to 7 within 8 seconds.
3.Release bonnet [hood] switch.
4.Switch ignition ON.
5.Lock doors.
6.Switch ignition OFF.
7.Switch ignition ON.
If alarm is correctly accessed, horn will sound and
LED will flash. The following checks can be made:
8.Open and close any door or tailgate - LED will
light.
9.Depress bonnet [hood] switch - hazards will
flash.
10.Check engine cranking is disabled. Do not turn
off ignition.
11.Check ultrasonic by operating handset, LED will
emit one 5 second flash, and will flash if interior
is disturbed.
NOTE: If ECU is new born mode any
handset of the right frequency will work. If
not an initialised handset is required see
Handset Initialisation.
12.Turn OFF ignition or press handset to end test
procedure. Horn will sound as before to indicate
end of test mode.

ELECTRICAL
1
FAULT DIAGNOSIS GENERAL INFORMATION
The electrical fault diagnostic tool on Discovery
vehicles is Testbook. Detailed information of electrical
systems, component locations and circuit diagrams
are covered in the Discovery Electrical
Troubleshooting Manual.
See INTRODUCTION,
Information, Fault Diagnostic Equipment
This section covers checks of the charging and
ignition system.
GENERATOR TESTING
Service repair no - 86.10.01
Charging system check
1.Check battery is in good condition, with an open
circuit voltage of at least 12.6 V. Recharge or
substitute battery to carry out test.
2.Check drive belt condition.
See SECTION 10,
Maintenance, Under Bonnet [Hood]
Maintenance
3.Check battery connections are clean and tight.
4.Check generator connections are clean and
tight.
5.Ensure there is no drain on battery from, for
example, interior, under bonnet [hood] or door
edge lamps.
Generator test
Following instructions refer to use of suitable test
equipment using a carbon pile rheostat.
6.Connect test equipment referring to
manufacturer's instructions.
7.Start engine and run at 3000 rev/min without
accessory load.
8.Rotate carbon pile load control to achieve
greatest output (amps) without allowing voltage
to fall below 12.0 V. A reading in amps, of
generator output, minus 10% to allow for EFI
and Ignition loss, should be obtained.
9.Run engine at 3000 rev/min, switch selector to
regulator test, read voltmeter. A reading of 13.6
to 14.4 V should be obtained.
10.Switch selector to diode/stator test, switch on
headlamps to load generator. Raise engine
speed to 3000 rev/min, read voltmeter, needle
must be within 'OK' range.TESTING IN POSITION
Charging circuit resistance test.
1.Connect a low range voltmeter between
generator terminal marked B+ and positive
terminal of battery.2.Switch on headlamps, start engine. Run engine
at approximately 3000 rev/min. Note voltmeter
reading.
3.Transfer voltmeter connections to frame of
generator and negative terminal of battery, and
again note voltmeter reading.
4.If reading exceeds 0.5 volt on positive side or
0.25 volt on negative side, there is a high
resistance in charging circuit which must be
traced and remedied.